At the A1 level, you can think of '不規則な' (fukisoku-na) as a way to say 'not regular' or 'messy timing.' Beginners usually learn the word '規則' (kisoku) which means 'rule.' By adding '不' (fu) to the beginning, it means 'no rule.' You might use this when talking about your daily life. For example, if you eat breakfast at 7 AM one day and 11 AM the next day, that is 'fukisoku.' It is a useful word to explain why you are tired or why your schedule is difficult. Just remember to add 'na' when you put it before a noun like 'lifestyle' (seikatsu) or 'meals' (shokuji). You don't need to know the complex kanji yet, but recognizing '不' as 'not' is very helpful for many Japanese words. Focus on the phrase 'Fukisoku na seikatsu' (irregular life) as your main example at this level.
At the A2 level, you start using '不規則な' to describe more than just your sleep schedule. You can use it to describe shapes, sounds, or patterns you see around you. For example, 'Fukisoku na katachi' means an irregular shape, like a rock or a cloud. You will also see this word in basic grammar lessons when talking about 'Fukisoku doushi' (irregular verbs). In Japanese, verbs like 'suru' and 'kuru' are irregular. Understanding this word helps you categorize how things work—some things follow a rule (kisoku-teki), and some things do not (fukisoku). You should practice making simple sentences like 'Watashi no shigoto wa jikan ga fukisoku desu' (My work hours are irregular). This is a common way to explain why you might be late or busy at different times.
At the B1 level, '不規則な' becomes a key vocabulary word for discussing health, society, and work-life balance. You are expected to use it in more complex sentences using 'node' or 'kara' to explain cause and effect. For example: 'Fukisoku na seikatsu o tsuzuketa node, taicho o kuzushite shimatta' (Because I continued an irregular lifestyle, I lost my health). You should also distinguish 'fukisoku' from similar words like 'midareta' (disordered). While 'midareta' might imply a lack of discipline, 'fukisoku' can simply be a fact of the job, such as for a nurse or a pilot. At this level, you should be comfortable using the adverbial form 'fukisoku ni' to describe how things change or move, such as 'Fukisoku ni fureru' (to shake irregularly).
At the B2 level, you will encounter '不規則な' in more professional and academic texts. It is used to describe economic fluctuations, biological rhythms (like circadian rhythms), and complex linguistic patterns. You should understand the nuance that 'fukisoku' implies a lack of predictable periodicity. In business, 'fukisoku na juyou' (irregular demand) is a common term for products that don't have a steady sales cycle. You should also be able to use the word in the context of 'fukisoku hatsugen' (out-of-order remarks) in formal settings like a parliament or a board meeting. At this stage, you should be able to discuss the pros and cons of an irregular schedule using formal structures like 'fukisoku de aru koto no demeritto' (the disadvantages of being irregular).
At the C1 level, your understanding of '不規則な' should include its use in abstract and philosophical contexts. You might read about 'fukisoku na bi' (the beauty of irregularity) in Japanese aesthetics, where asymmetry and unpredictability are valued over perfect regularity. You will see it in high-level scientific papers discussing 'fukisoku na nendo' (irregular viscosity) or 'fukisoku na kesshou' (irregular crystals). You should be able to use the word to describe subtle deviations in social trends or historical patterns. Furthermore, you should be able to contrast 'fukisoku' with 'hensoku' (anomalous) and 'reigai' (exception) with precision, choosing the exact word that fits the context of a system's failure versus a system's inherent variability.
At the C2 level, '不規則な' is used with complete native-like precision in highly specialized fields. This includes stochastic processes in mathematics, where 'fukisoku' describes the randomness of variables, or in literary analysis to describe the 'fukisoku na rizumu' (irregular rhythm) of modern poetry that intentionally breaks traditional '5-7-5' structures. You should be able to engage in deep discussions about how 'fukisoku' elements in urban planning contribute to or detract from a city's 'livability.' At this level, the word is not just a descriptor but a tool for analyzing the fundamental nature of chaos and order in the universe. You can seamlessly integrate it into complex rhetorical structures, using it to highlight the tension between human-made rules and the inherent 'fukisoku' nature of the physical world.

不規則な in 30 Seconds

  • Means 'irregular' or 'unsystematic.'
  • Used for schedules, health, and grammar.
  • A na-adjective (needs 'na' before nouns).
  • Opposite of 'kisoku-teki' (regular).

The Japanese word 不規則な (ふきそくな - Fukisoku-na) is a versatile na-adjective that translates primarily to 'irregular,' 'unsystematic,' or 'erratic.' At its core, it describes any state, action, or object that lacks a consistent pattern, deviates from established rules, or occurs at unpredictable intervals. In Japanese society, where punctuality and routine are often highly valued, this word carries a significant weight when describing lifestyles, biological rhythms, or technical anomalies.

Lifestyle and Health
This is perhaps the most common daily usage. It describes 'Fukisoku na seikatsu' (an irregular lifestyle), referring to inconsistent sleeping patterns, eating at odd hours, or lack of routine. Doctors frequently use this term when advising patients to stabilize their daily habits to improve health.

最近、仕事が忙しくて不規則な生活が続いています。(Lately, work has been busy, and I've been leading an irregular lifestyle.)

Scientific and Technical Contexts
In mathematics, physics, or linguistics, it refers to deviations from standard laws or paradigms. For example, 'Fukisoku doushi' (irregular verbs) in grammar, or 'Fukisoku na chindou' (irregular vibrations) in mechanical engineering. It implies a departure from the 'Kisoku' (rule).

Beyond just 'messy,' the word implies a lack of 'system.' If a train schedule changes randomly, it is 'fukisoku.' If your heart beats out of rhythm, it is 'fukisoku.' It is a clinical yet descriptive term used in both professional diagnoses and casual complaints about one's busy schedule. Because it is a na-adjective, it requires 'na' before a noun and 'da' or 'desu' to end a sentence. It is less about being 'wrong' and more about being 'non-sequential' or 'non-periodic.' In the context of nature, it might describe the irregular shape of a stone or the unpredictable gusts of wind during a storm.

Using 不規則な correctly requires understanding its role as a 'na-adjective' (keiyou-doushi). This means it behaves like a noun in some ways but acts as an adjective to modify other nouns. Grammatically, you will most often see it in the pattern [Adjective] + な + [Noun]. For example, 'Fukisoku na nichi-jyo' (An irregular daily life).

Modifying Nouns
When you want to describe a noun as irregular, always include 'na'. Example: 不規則な食事 (Fukisoku na shokuji - irregular meals). This describes meals taken at different times every day.

不規則な勤務時間のせいで、友達となかなか会えません。(Because of irregular work hours, I can't really meet my friends.)

As a Predicate
To say something 'is irregular,' drop the 'na' and add 'da' or 'desu'. Example: 彼の鼓動は不規則だ (Kare no kodou wa fukisoku da - His heartbeat is irregular).

When discussing abstract concepts like 'irregular change,' use 'Fukisoku na henka.' In a business meeting, you might hear 'Fukisoku na juyou' (irregular demand), meaning demand that doesn't follow seasonal or weekly trends. It is important to note that while 'Fukisoku' is the noun form (irregularity), it is almost always paired with 'na' in descriptive speech. In negative form, it becomes 'Fukisoku dewa nai' (is not irregular). In past tense, 'Fukisoku datta' (was irregular). Using it in the middle of a sentence to connect ideas requires the 'de' form: 'Seikatsu ga fukisoku de, karada o kowashita' (My lifestyle was irregular, and I ruined my health).

You will encounter 不規則な in a variety of real-world settings, ranging from the clinic to the computer lab. It is a 'standard' word—not too formal, not too casual—making it a staple of adult Japanese vocabulary. In the workplace, it is the go-to word for describing shifts that aren't 9-to-5.

At the Doctor's Office (Naika/Internal Medicine)
A doctor might ask, 'Suimin wa fukisoku desu ka?' (Is your sleep irregular?). It is a key term in medical history taking, specifically regarding pulse (myakuhaku), digestion (benpi/geri), and sleep (suimin).

心拍数が不規則な場合は、すぐに精密検査を受けてください。(If your heart rate is irregular, please get a detailed check-up immediately.)

In Language Classrooms
Japanese teachers use this to describe verbs like 'kuru' (to come) and 'suru' (to do), which are 'Fukisoku doushi.' It is a fundamental term for anyone studying the mechanics of language.

In design or art, you might hear it used to describe a 'natural' look. 'Fukisoku na moyou' (irregular patterns) can be seen as beautiful in the context of 'Wabi-sabi,' where perfection is avoided. However, in most logistical contexts, 'fukisoku' is a problem to be solved. If a bus arrives at 'fukisoku na kankaku' (irregular intervals), passengers will be frustrated. On social media, people often complain about their 'fukisoku na seikatsu' when they stay up late gaming or working, using it as a synonym for 'messy lifestyle' or 'poor self-discipline.'

While 不規則な is straightforward, English speakers often confuse it with other 'negative' adjectives or use it where a more specific word is required. The most common error is using it to mean 'strange' or 'weird' (okashii/hen). 'Fukisoku' specifically refers to the *pattern* or *timing*, not the *nature* of the thing itself.

Mistake: Confusing with 'Midareta' (Disordered)
While 'Fukisoku na seikatsu' is correct, 'Midareta seikatsu' implies a more moral or chaotic breakdown of life. 'Fukisoku' is more clinical; 'Midareta' is more judgmental or visual.

× 部屋が不規則な状態です。(The room is in an irregular state.)
○ 部屋が散らかっています。(The room is messy.)

Mistake: Forgetting the 'Na'
Since 'Fukisoku' is a na-adjective, saying 'Fukisoku seikatsu' (without the na) is grammatically incomplete in standard Japanese, though it might appear in compound nouns in technical writing.

Another nuance is the difference between 'Fukisoku' and 'Tokubetsu' (special). If a train stops at a station it usually skips, that is 'Tokubetsu' or 'Rinji' (temporary/extra), not necessarily 'Fukisoku' unless the pattern of stopping is random. Learners also sometimes use 'Fukisoku' to describe a person's personality (e.g., an 'irregular person'). This is incorrect. To describe an unpredictable person, use 'Kimagure' (fickle/whimsical). 'Fukisoku' is strictly for systems, rhythms, shapes, and schedules.

To truly master 不規則な, you must see how it sits alongside its synonyms. Depending on whether you are talking about a broken rhythm, an unusual rule, or a messy lifestyle, there might be a better word choice.

不定 (Futei) vs. 不規則 (Fukisoku)
'Futei' means 'indefinite' or 'undetermined.' Use 'Futei' for things that haven't been decided yet (like an indefinite date). Use 'Fukisoku' for things that *have* a pattern, but the pattern is inconsistent.
変則 (Hensoku) vs. 不規則 (Fukisoku)
'Hensoku' (irregular/anomalous) is often used for non-standard methods or rules. For example, a 'Hensoku-teki na houhou' (an irregular/unorthodox method). While 'Fukisoku' is about rhythm/pattern, 'Hensoku' is about the deviation from a standard procedure.

Comparison:
1. 不規則な動き (Fukisoku na ugoki) - Erratic movement (physics/rhythm).
2. 変則的な動き (Hensoku-teki na ugoki) - Unorthodox movement (strategy/sports).

乱れた (Midareta) vs. 不規則 (Fukisoku)
'Midareta' (disordered/disturbed) suggests that something that *should* be orderly has been broken. 'Fukisoku' is more neutral. If the wind blows irregularly, it's 'Fukisoku.' If your hair is messy, it's 'Midareta.'

In summary, use 'Fukisoku' when you want to emphasize the lack of a 'Kisoku' (rule/pattern). Use 'Hensoku' for deviations from 'standard' ways, and 'Midareta' for things that have become chaotic or messy. For example, 'Fukisoku doushi' is the standard linguistic term; you would never say 'Midareta doushi' for an irregular verb, as that would imply the verb is behaving 'badly' or 'immorally' rather than just having a different conjugation pattern.

Fun Fact

The kanji '規' originally depicted a person holding a compass to draw a circle, while '則' depicted a knife used to carve rules onto bronze vessels. Together with '不', it literally means 'not carved according to the compass.'

Pronunciation Guide

UK ɸɯkʲisokɯ na
US fu-ki-so-ku na
Japanese is mora-timed, so each syllable (fu-ki-so-ku) gets equal length.
Rhymes With
Kisoku (Rule) Hensoku (Irregularity) Zoku (Tribe) Kozoku (Ancient) Shizoku (Clan) Keizoku (Continuation) Soku (Fast) Chokusoku (Direct)
Common Errors
  • Pronouncing 'fu' like 'foo' with rounded lips.
  • Over-emphasizing the 'u' in 'ku'.
  • Forgetting to add 'na' when modifying a noun.
  • Incorrect pitch accent leading to confusion with other 'fu' words.
  • Merging 'soku' into a single syllable.

Examples by Level

1

不規則な生活は体に悪いです。

An irregular lifestyle is bad for the body.

不規則な (na-adjective) + 生活 (noun)

2

私の食事は不規則です。

My meals are irregular.

Topic + は + 不規則 (adjective) + です

3

不規則な形の石があります。

There is an irregularly shaped stone.

不規則な (na-adj) + 形 (noun) + の (particle) + 石 (noun)

4

不規則な時間に電話が来ます。

Calls come at irregular times.

不規則な + 時間 (time) + に (at)

5

彼は不規則な仕事が好きではありません。

He doesn't like irregular work.

不規則な + 仕事 (work) + が (particle) + 好きではない (dislike)

6

不規則なリズムで踊ります。

I dance to an irregular rhythm.

不規則な + リズム (rhythm) + で (with/to)

7

このバスは不規則に来ます。

This bus comes irregularly.

不規則に (adverbial) + 来ます (verb)

8

不規則な休みがあります。

I have irregular holidays.

不規則な + 休み (break/holiday)

1

日本語には不規則な動詞が二つあります。

There are two irregular verbs in Japanese.

不規則な + 動詞 (verb)

2

不規則な生活を直したいです。

I want to fix my irregular lifestyle.

不規則な + 生活 + を + 直したい (want to fix)

3

不規則な模様のシャツを買いました。

I bought a shirt with an irregular pattern.

不規則な + 模様 (pattern)

4

雨が不規則に降っています。

The rain is falling irregularly.

不規則に (adverb) + 降る (to fall)

5

不規則な心拍を感じました。

I felt an irregular heartbeat.

不規則な + 心拍 (heartbeat)

6

彼の休みは不規則なので、会うのが難しいです。

Because his days off are irregular, it's hard to meet him.

不規則 + なので (because)

7

不規則な動きをするおもちゃです。

It's a toy that moves irregularly.

不規則な + 動き (movement)

8

不規則な食事は太る原因になります。

Irregular meals cause weight gain.

不規則な + 食事 + は + 原因 (cause) + になる

1

不規則な生活を続けていると、病気になるリスクが高まります。

If you continue an irregular lifestyle, the risk of getting sick increases.

不規則な + 生活 + を + 続けている (continuing)

2

不規則なシフトで働いているので、睡眠不足です。

I am sleep-deprived because I work irregular shifts.

不規則な + シフト (shift)

3

この海岸線は不規則な形をしています。

This coastline has an irregular shape.

不規則な + 形 + をしている (to have a shape)

4

経済の不規則な変動を予測するのは難しい。

It is difficult to predict irregular fluctuations in the economy.

不規則な + 変動 (fluctuation)

5

不規則な動詞の活用を覚えるのは大変です。

Learning the conjugation of irregular verbs is hard.

不規則な + 動詞 + の + 活用 (conjugation)

6

機械から不規則な音が聞こえてきました。

An irregular sound started coming from the machine.

不規則な + 音 (sound)

7

不規則な勤務形態がストレスの原因になっています。

Irregular working patterns are becoming a cause of stress.

不規則な + 勤務形態 (working pattern)

8

不規則な点滅を繰り返すライトが気になります。

The light that keeps flashing irregularly bothers me.

不規則な + 点滅 (flashing)

1

現代社会では、不規則な生活を余儀なくされる人が増えています。

In modern society, more people are forced to lead irregular lives.

余儀なくされる (to be forced to do)

2

この植物は不規則な間隔で花を咲かせます。

This plant blooms at irregular intervals.

不規則な + 間隔 (interval)

3

不規則なデータの集まりから法則性を見つけ出す。

Find a pattern from a collection of irregular data.

不規則な + データ (data)

4

台風の影響で、不規則な風が吹き荒れています。

Due to the typhoon, irregular winds are blowing wildly.

不規則な + 風 (wind)

5

不規則な振動が橋の構造に悪影響を及ぼしている。

Irregular vibrations are having a negative impact on the bridge's structure.

悪影響を及ぼす (to exert a bad influence)

6

国会で不規則な発言があり、審議が中断しました。

There were out-of-order remarks in the Diet, and deliberations were suspended.

不規則な + 発言 (remarks/speech)

7

不規則な天候のせいで、農作物の収穫が遅れています。

Due to irregular weather, the harvest of crops is delayed.

不規則な + 天候 (weather)

8

彼は不規則な生活習慣を改善するためにジムに通い始めた。

He started going to the gym to improve his irregular lifestyle habits.

不規則な + 生活習慣 (lifestyle habits)

1

生物の進化において、不規則な変異が重要な役割を果たすことがある。

In biological evolution, irregular mutations can play an important role.

不規則な + 変異 (mutation)

2

その建築家は、あえて不規則な線を多用することで自然との調和を図った。

The architect aimed for harmony with nature by intentionally using many irregular lines.

あえて (daringly/intentionally)

3

市場の不規則な動きは、投資家の心理状態を反映している。

The irregular movements of the market reflect the psychological state of investors.

反映している (reflecting)

4

不規則な韻律を持つ詩は、読者に強い印象を与える。

Poetry with irregular meter leaves a strong impression on the reader.

不規則な + 韻律 (meter/rhythm in poetry)

5

脳波の不規則な乱れが、てんかんの発作を引き起こす。

Irregular disturbances in brain waves trigger epileptic seizures.

不規則な + 乱れ (disturbance)

6

不規則な地層の重なりから、過去の地殻変動を読み解く。

Decipher past crustal movements from the irregular overlapping of geological layers.

読み解く (to decipher)

7

不規則な雇用形態の広がりが、社会不安の一因となっている。

The spread of irregular employment patterns is a contributing factor to social unrest.

一因となっている (is one cause)

8

星々の不規則な配置の中に、古代の人々は星座を見出した。

In the irregular arrangement of stars, ancient people discovered constellations.

不規則な + 配置 (arrangement)

1

カオス理論によれば、一見不規則な現象の背後には複雑な秩序が隠されている。

According to chaos theory, a complex order is hidden behind seemingly irregular phenomena.

一見 (at first glance)

2

不規則なパルス信号を解析することで、深宇宙からのメッセージを探る。

By analyzing irregular pulse signals, we search for messages from deep space.

不規則な + パルス信号 (pulse signals)

3

不規則な都市開発が、結果として独特の景観美を生み出している。

Irregular urban development has, as a result, created a unique landscape beauty.

結果として (as a result)

4

言語の不規則な変化は、文化の混淆や歴史的背景を物語っている。

Irregular changes in language tell the story of cultural blending and historical backgrounds.

物語っている (to tell/illustrate)

5

不規則な熱運動がミクロな世界での物質の挙動を支配している。

Irregular thermal motion governs the behavior of matter in the microscopic world.

挙動 (behavior/movement)

6

不規則な分布を示す希少種の生態を長期間にわたって観察する。

Observe over a long period the ecology of rare species that show an irregular distribution.

長期間にわたって (over a long period)

7

法治国家において、不規則な法解釈は司法の信頼を揺るがしかねない。

In a constitutional state, irregular legal interpretations could undermine judicial trust.

揺るがしかねない (could potentially shake/undermine)

8

不規則な情報の断片を統合し、真実を炙り出すのは容易ではない。

It is not easy to integrate irregular fragments of information and bring the truth to light.

炙り出す (to bring to light/expose)

Common Collocations

不規則な生活
不規則な動詞
不規則な心拍
不規則な勤務
不規則な形
不規則なリズム
不規則な変動
不規則な間隔
不規則な発言
不規則な模様

Common Phrases

生活が不規則だ

— One's daily life/routine is irregular. Used to describe poor habits.

最近、生活が不規則で疲れが取れない。

不規則に並ぶ

— To be lined up or arranged without a specific order.

石が不規則に並んでいる。

時間が不規則だ

— The timing is inconsistent. Often used for work shifts.

この仕事は時間が不規則なので大変です。

不規則な変化

— Changes that don't follow a predictable curve or pattern.

気温の不規則な変化に注意してください。

不規則な動き

— Erratic or unpredictable movement.

虫が不規則な動きをしている。

不規則な食事

— Eating at inconsistent times. Often linked to health issues.

不規則な食事は胃に負担をかける。

不規則な睡眠

— Irregular sleep patterns.

不規則な睡眠はメンタルに影響する。

不規則な点滅

— Irregular flickering of lights.

信号が不規則な点滅を始めた。

不規則な振動

— Vibrations that lack a steady frequency.

エンジンから不規則な振動がする。

不規則な呼吸

— Irregular breathing patterns.

寝ている時の不規則な呼吸が心配だ。

Idioms & Expressions

"不規則な生活のツケ"

— The 'bill' or consequence of an irregular lifestyle. Usually refers to getting sick.

不規則な生活のツケが回ってきた。

Casual
"不規則極まりない"

— To be extremely irregular. 'Kiwamarinai' adds strong emphasis.

彼の生活は不規則極まりない。

Formal/Emphatic
"不規則な波"

— Often used metaphorically for the 'ups and downs' of life or luck.

人生は不規則な波のようだ。

Poetic
"不規則を絵に描いたような"

— The perfect example of irregularity. Literally 'like a picture of irregularity.'

彼は不規則を絵に描いたような生活をしている。

Idiomatic
"不規則な歩み"

— Metaphor for progress that is not steady or consistent.

不規則な歩みながらも前進している。

Literary
"不規則な連鎖"

— A chain reaction that occurs without a clear predictable pattern.

不規則な連鎖反応が起きた。

Technical
"不規則なリズムを刻む"

— To beat or pulse in an irregular way (often used for heart or music).

心臓が不規則なリズムを刻んでいる。

Literary
"不規則な光を放つ"

— To emit light irregularly (like a dying star or broken lamp).

その星は不規則な光を放っていた。

Literary
"不規則な分布"

— A distribution that shows no specific pattern (statistical).

人口が不規則な分布を見せている。

Academic
"不規則な足取り"

— Walking with an unsteady or irregular gait (often implies drunkenness or injury).

不規則な足取りで夜道を歩く。

Neutral

Word Family

Nouns

規則 (Kisoku) - Rule
不規則 (Fukisoku) - Irregularity
規則性 (Kisoku-sei) - Regularity

Verbs

規則化する (Kisoku-ka suru) - To regularize
規則に則る (Kisoku ni notottoru) - To follow rules

Adjectives

規則的な (Kisoku-teki na) - Regular
規則正しい (Kisoku tadashii) - Well-disciplined/regular

Related

例外 (Reigai) - Exception
変則 (Hensoku) - Anomaly
無秩序 (Muchitsujo) - Disorder
ランダム (Randamu) - Random
不定 (Futei) - Indefinite

Memorize It

Mnemonic

Imagine a 'Rule' (Kisoku) being broken by a giant 'X' (the 'Fu' of negation). Life is 'Fukisoku' when the 'Rule' is 'Not' ('Fu') there.

Visual Association

Visualize a heart rate monitor (EKG) with spikes at random intervals. That jagged line is the visual representation of 'Fukisoku.'

Word Web

Health Grammar Lifestyle Pattern Chaos Rule Schedule Shape

Challenge

Try to identify three things in your current room that have an 'irregular' (fukisoku) shape or pattern.

Word Origin

Composed of the prefix '不' (not), '規' (standard/compass), and '則' (rule/law). It entered the Japanese language via Classical Chinese roots.

Original meaning: Not according to the standard rules or measurements.

Sino-Japanese (Kango)

Cultural Context

Calling someone's life 'fukisoku' can be seen as a mild criticism of their self-discipline in Japan.

English speakers might say 'messy' or 'all over the place,' but 'Fukisoku' is more clinical and covers both lifestyle and physical patterns.

Fukisoku doushi (Irregular verbs) - Every Japanese student's nightmare. Fukisoku na kodou (Irregular Heartbeat) - A common title in medical dramas. Fukisoku na Tensai (Irregular Genius) - Often used to describe eccentric artists.
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