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B2 adjective #7,000 le plus courant 11 min de lecture

irracional

Top 7,000

Entraîne-toi Exemples Notes et astuces irracional en 30 secondes

Explication irracional in your Level:

At the A1 level, you can think of 'irracional' as a word that means 'not logical' or 'no tiene sentido' (doesn't make sense). Even though it's a B2 word, it's easy to understand because it looks like the English word 'irrational.' You might use it to describe something that seems very strange. For example, if someone says they are afraid of a tiny, harmless butterfly, you could say 'Es un miedo irracional.' At this stage, just focus on the fact that it describes something that isn't 'normal' or 'logical.' Remember that it doesn't change for boys or girls; it's always 'irracional.' Just add an 'es' to make it plural: 'Son irracionales.' It's a great 'big word' to impress your teacher with!

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At the A2 level, you're starting to describe things in more detail. You can use 'irracional' to talk about feelings and decisions. Instead of just saying 'es malo' (it's bad), you can say 'es una decisión irracional' (it's an irrational decision). This shows you understand that the decision wasn't made with a good plan. You can also start using it with simple intensifiers like 'muy' (very). 'Tu comportamiento es muy irracional.' Notice how it follows the noun: 'comportamiento irracional.' This is the standard position for adjectives in Spanish. You might also see it in simple math contexts, like when talking about numbers that never end.

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At the B1 level, you should be comfortable using 'irracional' to debate opinions. You can use it to describe abstract concepts like 'pensamientos' (thoughts) or 'creencias' (beliefs). It's a useful word for expressing disagreement in a more sophisticated way than simply saying 'no estoy de acuerdo.' For example, 'Esa teoría me parece un poco irracional because...' (That theory seems a bit irrational to me because...). You should also be aware of its common collocations, such as 'miedo irracional' or 'comportamiento irracional.' At this level, you can also start using the adverbial form 'irracionalmente' to describe actions, though 'de forma irracional' is often easier to use and sounds very natural.

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At the B2 level, which is the target level for this word, you are expected to use 'irracional' with precision across different contexts. You should understand the difference between 'irracional' (lacking reason entirely) and 'ilógico' (a specific flaw in reasoning). You can use it in academic or professional discussions, such as describing 'exuberancia irracional' in the stock market or 'conductas irracionales' in a sociological study. You should also be able to use the noun 'irracionalidad' to discuss the concept itself. Your pronunciation should be clear, especially the trilled 'rr' and the final 'l'. You can use it to add nuance to your arguments, showing that you can distinguish between what is reasonable and what is driven by impulse or emotion.

At the C1 level, 'irracional' becomes a tool for deep analysis. You can use it to explore complex philosophical or literary themes. You might discuss the 'dimensión irracional del ser humano' in a literature essay or analyze 'políticas irracionales' in a political science debate. You should be able to use it alongside advanced synonyms like 'descabellado,' 'insensato,' or 'arbitrario,' choosing the one that fits the exact tone of your discourse. You should also be familiar with how the concept of the irrational has been treated in Spanish culture, such as in the works of Unamuno or the Surrealist artists. Your usage should be fluid, natural, and contextually perfect, whether you're speaking formally or informally.

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At the C2 level, your mastery of 'irracional' is complete. You understand its deepest nuances, including its use in highly specialized fields like advanced mathematics (irrational numbers), psychoanalysis, and existential philosophy. You can use the word to critique complex systems of thought, perhaps arguing that 'la razón pura puede llevar a resultados irracionales.' You are comfortable using the word in any register, from a heated street argument to a doctoral thesis. You can also play with the word's connotations, using it ironically or to highlight the beauty in the non-logical aspects of life. At this level, you don't just know the word; you know the entire intellectual history and emotional weight that the concept of 'lo irracional' carries in the Spanish language.

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Entraîne-toi Exemples Notes et astuces

irracional en 30 secondes

Irracional means lacking logic or reason, used for behavior, emotions, and math.
It is a B2 level adjective that is gender-neutral and ends in -al.
Commonly paired with words like 'miedo', 'comportamiento', and 'número'.
Its primary antonym is 'racional', and its noun form is 'irracionalidad'.

The Spanish word irracional is a powerful adjective that mirrors its English cognate 'irrational.' At its core, it describes anything that lacks a basis in reason, logic, or sound judgment. In the Spanish-speaking world, this term is frequently employed across various domains, from the cold precision of mathematics to the heated depths of human emotion. When you describe a person's behavior as irracional, you are suggesting that their actions are not governed by the typical rules of cause and effect or common sense. It often carries a slightly more formal or analytical weight than the word 'loco' (crazy), focusing specifically on the absence of 'razón' (reason).

Psychological Context: In psychology, it refers to fears or thoughts that have no objective basis in reality. For instance, a phobia is often described as a 'miedo irracional.' This implies that the person suffering from the fear knows, on some level, that the danger is minimal, yet the emotional response remains overwhelming.
Mathematical Context: In mathematics, a 'número irracional' is a real number that cannot be expressed as a simple fraction. Numbers like Pi (π) or the square root of two are classic examples. Here, the word is strictly technical and carries no negative connotation.

Sentir un odio irracional hacia alguien sin conocerlo es un prejuicio que debemos evitar.

Beyond these specific uses, irracional is used in daily conversation to criticize decisions that seem absurd. If someone decides to sell their house to buy a collection of vintage spoons, a friend might call that an 'acto irracional.' It suggests a departure from the shared social understanding of what is beneficial or sensible. It is a word that demands a justification; if something is labeled this way, it is usually because it defies the 'porqué' (the why) that we expect in human interaction. In literature and philosophy, Spanish authors often explore the tension between the 'racional' and the irracional, viewing the latter as a source of both chaos and profound artistic inspiration.

El mercado financiero a veces se comporta de manera irracional, ignorando los datos económicos básicos.

Economic Usage: Economists use the term 'exuberancia irracional' to describe periods when investors drive stock prices far above their actual value based on pure hype rather than fundamentals.

Culturally, the concept of the irrational is deeply embedded in Spanish art, notably in the Surrealist movement. Artists like Salvador Dalí sought to capture the irracional logic of dreams. Therefore, while the word often denotes a lack of sense, it can also point toward a deeper, subconscious truth that logic cannot reach. In everyday Spanish, you will hear it in news reports about 'crímenes irracionales' (senseless crimes) or in academic lectures discussing 'comportamientos irracionales' in sociology. It is a versatile tool for defining the boundaries of what we consider 'normal' or 'logical' in society.

Using irracional correctly in Spanish requires understanding its grammatical behavior as an adjective. Since it ends in '-al', it is gender-neutral. This means it stays the same whether it modifies a masculine noun like 'un pensamiento' or a feminine noun like 'una idea.' The only change it undergoes is for number; if the noun is plural, the adjective becomes irracionales. This simplicity makes it a favorite for learners who are still mastering gender agreement.

With 'Ser' vs 'Estar': Most commonly, irracional is used with the verb 'ser' because it usually describes an inherent quality of an idea, a number, or a behavior. For example, 'Su miedo es irracional' (His fear is irrational). Using 'estar' is rare and would imply a temporary state of being irrational, which is usually expressed by other phrases like 'está actuando de forma irracional.'

No trates de razonar con él ahora; su postura es totalmente irracional.

Placement is also key. In standard Spanish, adjectives usually follow the noun. 'Un comportamiento irracional' sounds natural and emphasizes the lack of logic. However, in poetic or highly emphatic speech, you might see it before the noun, though this is much less common for this specific word. When modifying a verb, we often use the adverbial form 'irracionalmente,' but you can also use the phrase 'de manera irracional' or 'de forma irracional' to add a bit more weight to the description.

Los números irracionales no pueden ser representados como una fracción de dos enteros.

Intensifiers: To strengthen the impact, Spanish speakers often use 'completamente,' 'totalmente,' or 'profundamente' before irracional. This is common when expressing frustration or disbelief.

In academic writing, you will see it paired with abstract nouns like 'pensamiento,' 'lógica,' 'impulso,' or 'reacción.' For example, 'El autor analiza el impulso irracional que lleva al protagonista a la ruina.' This usage highlights the word's role in dissecting human nature. Whether you are discussing a math problem or a messy breakup, irracional provides the precise vocabulary needed to describe the absence of the 'logos' or reason that we usually expect from the world around us.

You will encounter irracional in a variety of real-world settings across the Spanish-speaking world. In the news, it is frequently used by journalists and commentators to describe events that defy explanation. For example, after a sudden and senseless act of violence or a bizarre political decision, a news anchor might say, 'Estamos ante un acto de violencia puramente irracional.' This usage helps frame the event as something outside the bounds of civilized logic.

In the News: Reporters use it to describe market crashes or social phenomena that don't follow predicted patterns. You might hear: 'La subida de precios es totalmente irracional dado el estado de la economía.'
In Cinema and TV: In dramas and thrillers, characters often use this word during climactic arguments. A character might shout, '¡Tu odio hacia mi familia es irracional!' to highlight that the conflict is based on old grudges rather than current facts.

En la película, el protagonista lucha contra un terror irracional a la oscuridad.

In educational settings, specifically in science and math classrooms, you will hear it constantly. A teacher explaining the properties of circles will inevitably talk about 'el número irracional pi.' In philosophy or psychology lectures, students discuss 'el hombre como ser irracional,' debating whether humans are truly guided by logic or by hidden impulses. This academic frequency makes it a staple of the CEFR B2 level, as it is essential for high-level discussion and analysis.

La creencia en las supersticiones es un ejemplo de pensamiento irracional en la era moderna.

Socially, you might hear it in debates about sports or politics. Fans might describe their loyalty to a losing team as 'un amor irracional.' In this context, the word takes on a slightly more positive, or at least understandable, tone—it's about passion. Whether it's a doctor explaining a 'reacción irracional' to a medication or a friend complaining about an 'exigencia irracional' from their boss, the word is a bridge between the clinical and the personal, used to mark the point where logic ends and something else begins.

One of the most common mistakes English speakers make when learning irracional is mispronunciation. In English, the 'i' is often short and the 'r' is soft. In Spanish, the 'i' must be a sharp 'ee' sound, and the 'rr' must be a distinct trill. Failing to trill the 'rr' can make the word sound unclear to native speakers. Another phonological trap is the 'a' sound; ensure it is the open 'ah' sound typical of Spanish, not the reduced vowel sound often heard in English.

False Prefixes: Sometimes learners try to create the opposite of 'racional' by using 'un-' or 'des-'. They might say 'unracional' or 'desracional.' These are incorrect. The only valid prefix for this word is 'ir-', following the Latin rule where 'in-' becomes 'ir-' before an 'r'.
Confusion with 'Ilógico': While often used as synonyms, 'ilógico' specifically refers to a flaw in a sequence of reasoning, whereas irracional often refers to the total absence of reason or an emotional state. Calling a math error 'irracional' is usually wrong; it's 'ilógico' or simply 'incorrecto.' Save irracional for numbers or for deeper, more systemic lack of reason.

Incorrecto: Es una idea desracional.
Correcto: Es una idea irracional.

Gender agreement is another area where mistakes occur, though ironically, by overthinking it. Because irracional is gender-neutral, some students mistakenly try to change the ending to '-o' or '-a' (e.g., 'una idea irracionala'). Remember that adjectives ending in '-al' do not change for gender. 'El plan irracional' and 'la decisión irracional' are both correct. Always check the plural form as well; it must be irracionales, adding '-es' to the consonant ending, not just '-s'.

Incorrecto: Sus miedos son irracionals.
Correcto: Sus miedos son irracionales.

Finally, avoid using irracional as a noun unless you are using the mathematical term 'un irracional.' In most contexts, you should use the noun 'irracionalidad' to describe the concept of being irrational. For example, 'La irracionalidad de la guerra' (The irrationality of war). Using the adjective as a noun in general conversation (e.g., 'Hizo una irracional') sounds awkward and incomplete to a native speaker.

Spanish offers a rich palette of words that share a semantic space with irracional, each with its own nuance. Understanding these alternatives will help you sound more like a native speaker and allow you to tailor your message to the specific situation. While irracional is the most direct and formal way to describe a lack of reason, other words might be more appropriate depending on whether you want to emphasize absurdity, lack of common sense, or a disconnect from logic.

Absurdo: Use 'absurdo' when something is so irrational that it becomes ridiculous or nonsensical. It often implies a level of silliness or impossibility. 'Es absurdo pensar que puedes volar batiendo los brazos.'
Ilógico: This is the best choice for errors in reasoning. If a conclusion doesn't follow from the premises, it is 'ilógico.' It is more clinical and less emotional than irracional.
Insensato: This word specifically targets a lack of 'sensatez' (good judgment). It is often used to describe people or actions that are reckless or unwise. 'Fue un acto insensato cruzar el río durante la tormenta.'

Comparación: Un número irracional (técnico), un argumento ilógico (error de razonamiento), una propuesta absurda (ridícula).

Other powerful alternatives include 'descabellado' and 'disparatado.' 'Descabellado' literally means 'without hair' but figuratively means 'hair-brained' or 'wildly unreasonable.' It’s great for describing crazy ideas or plans. 'Disparatado' comes from 'disparate' (nonsense) and is used for things that are completely out of touch with reality. In a more formal or literary context, you might use 'irrazonable,' which is a direct synonym for 'unreasonable' and is often used in legal or ethical discussions regarding what a 'reasonable person' would do.

Esa es una idea descabellada que nunca funcionará en la práctica.

Incoherente: When someone's irrationality manifests as a lack of connection between their words, they are 'incoherente.' This is common when someone is very angry or confused.

Finally, 'arbitrario' is a useful alternative when the irrationality comes from a lack of a fair or consistent rule. If a boss gives a promotion based on a coin flip, that is 'irracional' because it lacks logic, but it is specifically 'arbitrario' because it is based on whim rather than merit. By choosing between these synonyms, you can express exactly why something is lacking in reason, making your Spanish much more precise and expressive.

How Formal Is It?

Le savais-tu ?

The term was famously used in ancient Greece to describe numbers like the square root of 2, which supposedly caused a crisis in the Pythagorean school because it challenged their belief that everything could be explained by whole numbers.

Guide de prononciation

UK /ɪˈræʃ.ən.əl/

US /ɪˈræʃ.ən.əl/

The stress in Spanish is on the last syllable: i-rra-cio-NAL.

Rime avec

nacional racional final canal especial oficial natural total

Erreurs fréquentes

Pronouncing the 'i' like the 'i' in 'it' instead of 'ee' in 'see'.
Failing to trill the double 'rr'.
Adding a 'sh' sound to the 'ci' (it should be 'sy' or 'th' depending on region).
Placing the stress on the second-to-last syllable.
Not pronouncing the final 'l' clearly.

Niveau de difficulté

Lecture 2/5

Easy to recognize due to being a cognate with English 'irrational'.

Écriture 3/5

Requires correct spelling (double 'rr') and pluralization (-es).

Expression orale 4/5

Challenging due to the trilled 'rr' and the stress on the last syllable.

Écoute 3/5

Easy to understand if the listener is aware of the 'rr' sound.

Quoi apprendre ensuite

Prérequis

razón lógica miedo idea número

Apprends ensuite

irracionalidad racionalizar insensato descabellado absurdo

Avancé

epistemología onírico dialéctica praxis inherente

Grammaire à connaître

Adjectives ending in -al are gender-neutral.

El hombre irracional / La mujer irracional.

Plural of nouns/adjectives ending in a consonant add -es.

Irracional -> Irracionales.

The prefix 'in-' becomes 'ir-' before words starting with 'r'.

In + racional = Irracional.

The neuter article 'lo' turns adjectives into abstract nouns.

Lo irracional (The irrational part/concept).

Adjectives usually follow the noun in Spanish.

Un miedo irracional.

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Exemples par niveau

Su miedo es irracional.

His fear is irrational.

Uses 'ser' for an inherent quality.

No es una idea irracional.

It is not an irrational idea.

Negative construction with 'no'.

Es un número irracional.

It is an irrational number.

Technical use in math.

Ellos son irracionales.

They are irrational.

Plural agreement (irracionales).

¡Qué cosa más irracional!

What an irrational thing!

Exclamatory sentence.

Mi gato tiene un odio irracional al agua.

My cat has an irrational hatred of water.

Modifies the noun 'odio'.

Esa regla es irracional.

That rule is irrational.

Adjective follows the noun 'regla'.

Tengo un pensamiento irracional.

I have an irrational thought.

Simple adjective-noun pair.

A veces tomo decisiones irracionales.

Sometimes I make irrational decisions.

Plural adjective modifying 'decisiones'.

Es irracional estar enojado por eso.

It is irrational to be angry about that.

'Es irracional' + infinitive.

Su respuesta me pareció un poco irracional.

His answer seemed a bit irrational to me.

Use of 'parecer' as a linking verb.

No quiero actuar de forma irracional.

I don't want to act in an irrational way.

Adverbial phrase 'de forma irracional'.

Es un comportamiento irracional para un niño.

It is irrational behavior for a child.

Prepositional phrase 'para un niño'.

Ella tiene una preocupación irracional por el futuro.

She has an irrational worry about the future.

Feminine noun 'preocupación' but same adjective form.

Los precios en esa tienda son irracionales.

The prices in that store are irrational.

Plural subject and adjective.

No hay una explicación irracional para esto.

There isn't an irrational explanation for this.

Double negative sense (there is a logical one).

A pesar de las pruebas, él mantiene su creencia irracional.

Despite the evidence, he maintains his irrational belief.

Use of 'a pesar de' to show contrast.

Es irracional gastar todo el dinero en un solo día.

It is irrational to spend all the money in a single day.

Impersonal 'es' + adjective + infinitive.

Me di cuenta de que mi reacción fue irracional.

I realized that my reaction was irrational.

Past tense 'fue' with 'darse cuenta'.

No podemos basar nuestra política en impulsos irracionales.

We cannot base our policy on irrational impulses.

Noun 'impulsos' modified by 'irracionales'.

Es totalmente irracional pensar que el problema se resolverá solo.

It is totally irrational to think that the problem will solve itself.

Intensifier 'totalmente' used before the adjective.

Su miedo a volar es irracional pero muy común.

His fear of flying is irrational but very common.

Contrast using 'pero'.

La película explora el lado irracional de la naturaleza humana.

The movie explores the irrational side of human nature.

Abstract concept 'el lado irracional'.

Esa es una exigencia irracional de parte de tu jefe.

That is an irrational demand on your boss's part.

Phrase 'de parte de' (on behalf of/from).

El pánico irracional se apoderó de la multitud tras el ruido.

Irrational panic seized the crowd after the noise.

Subject-adjective agreement with 'pánico'.

Debemos distinguir entre una duda razonable y una sospecha irracional.

We must distinguish between a reasonable doubt and an irrational suspicion.

Direct contrast between antonyms.

La exuberancia irracional del mercado llevó a la burbuja económica.

The market's irrational exuberance led to the economic bubble.

Set phrase 'exuberancia irracional'.

Resulta irracional ignorar las advertencias de los científicos.

It turns out to be irrational to ignore scientists' warnings.

Use of 'resultar' instead of 'ser' for emphasis.

Su argumento carece de lógica; es puramente irracional.

His argument lacks logic; it is purely irrational.

Use of 'puramente' as a modifier.

A menudo, el amor se describe como un sentimiento irracional.

Often, love is described as an irrational feeling.

Passive voice 'se describe'.

No dejes que tus miedos irracionales limiten tu potencial.

Don't let your irrational fears limit your potential.

Imperative 'no dejes' with plural adjective.

Es un planteamiento irracional que no tiene sustento teórico.

It is an irrational approach that has no theoretical basis.

Relative clause 'que no tiene...'.

La obra de Dalí captura la esencia de lo irracional y lo onírico.

Dalí's work captures the essence of the irrational and the dreamlike.

Use of 'lo' to create a neuter noun from an adjective.

La violencia irracional en el deporte es un reflejo de tensiones sociales.

Irrational violence in sports is a reflection of social tensions.

Complex sentence structure with social commentary.

Sería irracional negar el impacto del cambio climático en la actualidad.

It would be irrational to deny the impact of climate change today.

Conditional 'sería' for hypothetical/polite statement.

El existencialismo aborda la angustia ante un universo aparentemente irracional.

Existentialism addresses the anguish before an apparently irrational universe.

Academic vocabulary (existencialismo, angustia).

Aferrarse a tradiciones obsoletas puede ser un acto irracional de resistencia.

Clinging to obsolete traditions can be an irrational act of resistance.

Gerund phrase 'aferrarse a...' as the subject.

La fe, para algunos, es el salto irracional hacia lo desconocido.

Faith, for some, is the irrational leap toward the unknown.

Metaphorical use in a philosophical context.

Sus celos irracionales acabaron destruyendo la relación de años.

His irrational jealousy ended up destroying the years-long relationship.

Adjective modifying 'celos' (always plural in this sense).

El discurso estaba plagado de falacias e ideas irracionales.

The speech was riddled with fallacies and irrational ideas.

Use of 'plagado de' (riddled with).

La dialéctica de la Ilustración revela cómo la razón puede mutar en barbarie irracional.

The dialectic of Enlightenment reveals how reason can mutate into irrational barbarism.

High-level historical and philosophical reference.

El teorema de Incompletitud de Gödel sacudió los cimientos de la lógica aparentemente no irracional.

Gödel's Incompleteness Theorem shook the foundations of apparently non-irrational logic.

Double negative logic and complex subject.

La psique humana alberga impulsos irracionales que desafían cualquier intento de sistematización.

The human psyche harbors irrational impulses that defy any attempt at systematization.

Sophisticated verbs like 'albergar' and 'desafiar'.

Resulta paradójico que un sistema tan estructurado genere resultados tan irracionales.

It is paradoxical that such a structured system generates such irrational results.

Subjunctive 'genere' after 'resulta paradójico que'.

La literatura del absurdo se nutre de la confrontación con lo irracional de la existencia.

The literature of the absurd feeds on the confrontation with the irrationality of existence.

Use of 'se nutre de' (feeds on/is based on).

Una burocracia excesiva a menudo deviene en una estructura irracional e ineficiente.

Excessive bureaucracy often becomes an irrational and inefficient structure.

Use of the verb 'devenir' (to become/turn into).

El autor critica la fe ciega en el progreso como un mito irracional de la modernidad.

The author criticizes blind faith in progress as an irrational myth of modernity.

Appositive phrase 'como un mito...'.

La respuesta colectiva ante la crisis fue de una irracionalidad e histeria palpables.

The collective response to the crisis was of a palpable irrationality and hysteria.

Noun form 'irracionalidad' used for emphasis.

Synonymes

ilógico absurdo insensato descabellado disparatado irrazonable arbitrario incoherente

Antonymes

racional lógico razonable sensato

Collocations courantes

miedo irracional

número irracional

comportamiento irracional

odio irracional

decisión irracional

impulso irracional

creencia irracional

exuberancia irracional

reacción irracional

pensamiento irracional

Phrases Courantes

de manera irracional

— In an irrational manner. Used to describe how an action is performed.

Actuó de manera irracional durante la emergencia.

ser totalmente irracional

— To be completely irrational. Used for emphasis.

Esa propuesta es totalmente irracional.

caer en lo irracional

— To fall into the irrational. Used when a situation loses its logic.

La discusión cayó en lo irracional rápidamente.

un acto irracional

— An irrational act. Refers to a single specific non-logical event.

Fue un acto irracional de rebeldía.

postura irracional

— Irrational stance/position. Used in debates or politics.

Mantienen una postura irracional ante el conflicto.

lógica irracional

— Irrational logic. An oxymoron used to describe a twisted sense of reasoning.

Se rige por una lógica irracional propia.

temor irracional

— Irrational fear. Synonym for 'miedo irracional'.

Siente un temor irracional al fracaso.

conducta irracional

— Irrational conduct. Formal term for behavior.

La conducta irracional del sospechoso fue grabada.

amor irracional

— Irrational love. Describes a love that ignores all flaws or logic.

Siente un amor irracional por su país.

violencia irracional

— Irrational violence. Violence that seems to have no motive.

La ciudad sufrió una ola de violencia irracional.

Souvent confondu avec

irracional vs ilógico

Ilógico is specifically about a breakdown in reasoning steps, while irracional is about the total absence of reason.

irracional vs irrazonable

Irrazonable is often used for demands or prices that are unfair, while irracional is more about the internal logic.

irracional vs absurdo

Absurdo implies that something is so irrational it is laughable or impossible.

Expressions idiomatiques

"No tener ni pies ni cabeza"

— To have no rhyme or reason. Used when something is completely irrational or nonsensical.

Tu explicación no tiene ni pies ni cabeza.

informal

"Estar fuera de toda lógica"

— To be beyond all logic. Describes something purely irrational.

Esa decisión está fuera de toda lógica.

neutral

"Perder el juicio"

— To lose one's judgment/mind. Implies becoming irrational.

Parece que ha perdido el juicio con esa compra.

neutral

"Ser un despropósito"

— To be an absurdity or a blunder. Used for irrational actions.

Este nuevo impuesto es un despropósito.

neutral

"Ir contra toda razón"

— To go against all reason. Used for stubborn irrationality.

Su actitud va contra toda razón.

formal

"Hacer algo a tontas y a locas"

— To do something in a haphazard or irrational way.

No hagas el trabajo a tontas y a locas.

informal

"Sacar las cosas de quicio"

— To drive things out of joint/to exasperate. Often involves irrational reactions.

Tu actitud irracional me saca de quicio.

informal

"Ser harina de otro costal"

— To be a different kettle of fish. Used when comparing a rational vs irrational thing.

Eso ya es harina de otro costal, es algo irracional.

informal

"Dar palos de ciego"

— To strike out blindly. Describes acting without a rational plan.

La empresa está dando palos de ciego.

informal

"No tener sentido común"

— To lack common sense. A common way to describe irrationality.

Es irracional porque no tiene sentido común.

neutral

Facile à confondre

irracional vs irracional

Looks like 'irrational'.

In Spanish, it can also be a noun in math, and it never changes for gender.

Un número irracional.

irracional vs irrazonable

Similar meaning.

Irrazonable focuses on the lack of 'reasonableness' (fairness), while irracional focuses on the lack of 'rationality' (logic).

Un precio irrazonable.

irracional vs ilógico

Often used interchangeably.

Ilógico is about the rules of logic (A then B); irracional is about the state of being without reason.

Es ilógico que no traigas paraguas si llueve.

irracional vs insensato

Describes bad choices.

Insensato implies a lack of wisdom or common sense, often used for reckless actions.

No seas insensato, ponte el cinturón.

irracional vs descabellado

Describes crazy ideas.

Descabellado is more informal and implies an idea is totally 'off the rails'.

Un plan descabellado.

Structures de phrases

Es [adjetivo].

Es irracional.

Un/Una [sustantivo] [adjetivo].

Una idea irracional.

Es irracional + [verbo infinitivo].

Es irracional llorar por eso.

[Sustantivo] + ser + totalmente + irracional.

Su conducta es totalmente irracional.

Lo [adjetivo] de [sustantivo].

Lo irracional de su propuesta nos sorprendió.

Actuar de forma [adjetivo].

Actuó de forma irracional ante la crisis.

[Sustantivo] + carecer de + lógica + y ser + [adjetivo].

El plan carece de lógica y es irracional.

Aferrarse a lo [adjetivo].

Se aferra a lo irracional para no aceptar la verdad.

Famille de mots

Noms

irracionalidad (irrationality)

razón (reason)

racionalismo (rationalism)

racionalización (rationalization)

Verbes

racionalizar (to rationalize)

razonar (to reason)

Adjectifs

racional (rational)

razonable (reasonable)

razonado (reasoned)

Apparenté

lógica

sentido

juicio

absurdo

mente

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Comment l'utiliser

frequency

Common in academic, journalistic, and serious personal contexts.

Erreurs courantes

una idea irracionala → una idea irracional
Adjectives ending in -al do not change for gender.
pensamientos irracionals → pensamientos irracionales
To make it plural, you must add -es, not just -s.
un acto desracional → un acto irracional
The prefix for 'not rational' is 'ir-', not 'des-'.
su miedo es irracional (pronounced with English 'r') → su miedo es irracional (with trilled 'rr')
The double 'rr' in Spanish is always trilled.
Hizo un irracional. → Hizo algo irracional.
Irracional is an adjective, not a noun (except in math).

Astuces

Trill that RR

The double 'rr' in 'irracional' is the most important part of the pronunciation. If you don't trill it, it won't sound right to native speakers.

Gender Neutrality

Don't try to make it 'irracionala'. It stays 'irracional' for both masculine and feminine nouns.

Math vs. Life

Remember that in math, it's a technical term. In life, it's often a criticism or a description of strong emotion.

Use with 'Ser'

Stick with the verb 'ser' for this adjective, as it usually describes an inherent quality of an idea or person.

Abstract Nouns

Use 'lo irracional' to talk about the concept of the irrational in general. It's a very sophisticated-sounding structure.

Surrealism

If you are interested in Spanish art, look up how Dalí used 'lo irracional' in his paintings.

The 'IR' Prefix

Associate 'IR' with 'Incorrect Reason'. It's an easy way to remember the meaning.

Intensify It

Use 'totalmente irracional' to sound more natural when expressing a strong opinion.

Last Syllable Stress

Listen for the stress on the 'NAL'. This is the hallmark of Spanish adjectives ending in 'l'.

Avoid 'Desracional'

Never use 'des-' to negate this word. It's always 'irracional'.

Mémorise-le

Moyen mnémotechnique

Think of the 'IR' at the start as a 'Red Flag' for 'REASON'. If it has an 'IR', the reason is missing!

Association visuelle

Imagine a person trying to fit a square peg in a round hole while wearing a clown hat. This is an 'irracional' action.

Word Web

Razón Lógica Miedo Matemáticas Pi Absurdo Cerebro Emoción

Défi

Try to find three things today that you do out of habit but are actually 'irracionales' (like checking the fridge three times when you know it's empty).

Origine du mot

From the Latin 'irrationalis', which is formed by the prefix 'in-' (not) and 'rationalis' (pertaining to reason). The 'n' in 'in-' changed to 'r' to match the following 'r' for easier pronunciation.

Sens originel : Not based on reason or lacking the power of reason.

Romance (Latin-derived).

Contexte culturel

Avoid calling a person 'irracional' directly in a professional setting; it is better to say their 'postura' or 'planteamiento' is irracional.

In English, 'irrational' is often used as a synonym for 'crazy' or 'stupid' in casual speech. In Spanish, it remains slightly more formal.

Miguel de Unamuno's 'Del sentimiento trágico de la vida' discusses the irrational nature of faith. Salvador Dalí's 'The Conquest of the Irrational' (essay). The mathematical discovery of irrational numbers by Hippasus of Metapontum.

Pratique dans la vie réelle

Contextes réels

Mathematics

número irracional
decimales infinitos
no fraccionario
raíz cuadrada

Psychology

fobia irracional
impulso subconsciente
terapia cognitiva
creencia limitante

Economics

mercado irracional
burbuja financiera
pánico vendedor
decisión de consumo

Debates/Arguments

argumento sin lógica
postura absurda
falta de razón
punto de vista

Daily Life

miedo a la oscuridad
gastar dinero
actuar sin pensar
perder la cabeza

Amorces de conversation

"¿Crees que los humanos somos seres racionales o mayormente irracionales?"

"¿Cuál es tu miedo irracional más extraño?"

"¿Alguna vez has tomado una decisión irracional que terminó saliendo bien?"

"¿Crees que el amor es un sentimiento puramente irracional?"

"¿Qué comportamiento te parece el más irracional de la sociedad moderna?"

Sujets d'écriture

Describe una situación en la que actuaste de manera irracional. ¿Por qué crees que lo hiciste?

Reflexiona sobre un miedo irracional que tenías de niño y cómo lo superaste (o si aún lo tienes).

Escribe sobre una noticia reciente que te parezca un ejemplo de comportamiento irracional colectivo.

¿Cómo crees que el mundo sería diferente si nadie tuviera impulsos irracionales?

Explica el concepto de un número irracional a alguien que no sabe matemáticas, usando tus propias palabras.

Questions fréquentes

10 questions

Yes, but it is quite strong. Saying 'Eres irracional' suggests the person is incapable of thinking logically. It is more polite and precise to say 'Tu actitud es irracional' or 'Estás siendo irracional'.

It is both! Adjectives ending in '-al' do not change for gender. You say 'el plan irracional' and 'la idea irracional'.

The plural is 'irracionales'. You add '-es' because the word ends in a consonant.

The word is 'irracional'. 'Irracionable' is not a word in Spanish, though 'irrazonable' (unreasonable) is.

You can say 'irracionalmente', but it is also very common to say 'de manera irracional' or 'de forma irracional'.

Only in mathematics, where you can refer to 'un irracional' (an irrational number). In other cases, use 'la irracionalidad'.

Yes, but usually for things that are seriously illogical. For small, silly things, Spanish speakers might use 'tontería' or 'absurdo'.

It is a fear that has no logical basis, like being afraid of something harmless. It is the standard term for a phobia.

In math, it is neutral. In philosophy or art, it can sometimes be positive, referring to the power of the subconscious or human passion.

It is a strong trill, made by vibrating the tip of the tongue against the roof of the mouth. It is much stronger than the English 'r'.

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