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A1 verb #154 most common 8 min read

consider

Top 154

Practice it Examples Notes & Tips consider in 30 Seconds

Explanation consider in your Level:

At the A1 level, 'consider' is a word you use when you have to make a simple choice. Think about when you go to an ice cream shop. You see chocolate, vanilla, and strawberry. You look at them and think, 'Which one do I want?' That is considering. It is a slow way of thinking. You can use it to talk about your plans. For example, 'I consider going to the park today.' It helps you tell people that you are not sure yet, but you are thinking about it. It is also used to show you are a nice person. If you 'consider' your friends, you think about what they like. If your friend is tired, you consider them and stay quiet. It is a very helpful word for basic needs and feelings. You don't need to use big words with it. Just 'consider' + 'thing' or 'consider' + 'doing something.' It makes your English sound more thoughtful than just saying 'I think.' Even at this early stage, using 'consider' shows you are trying to express more complex ideas about your mind and your choices.

For A2 learners, 'consider' becomes useful for describing daily routines and small decisions in more detail. You might use it when talking about shopping or work. 'I am considering buying a new phone' is a perfect A2 sentence. It shows you understand the present continuous tense and how to use 'consider' with a gerund (-ing). At this level, you also start to see 'consider' in the passive voice, like 'It is considered polite to say thank you.' This helps you talk about social rules and culture. You can also use it to give gentle advice to others. Instead of saying 'Do this,' you can say 'You should consider doing this.' This makes you sound more polite and less bossy. You are also learning that 'consider' doesn't need the word 'about.' You don't say 'consider about the weather,' you just say 'consider the weather.' This is a key step in moving from basic translation to thinking in English. By using 'consider,' you can explain the reasons behind your actions more clearly to your teachers and friends.

At the B1 level, you start using 'consider' to express opinions and weigh pros and cons. You might say, 'I consider this book to be very interesting.' This structure (consider + object + to be) is more common as you reach intermediate levels. You also use it in more professional settings, such as writing a cover letter for a job: 'Please consider my application.' Here, it means 'look at my skills and think if I am right for the job.' You are also becoming aware of the word 'considerate' (the adjective) and how it relates to the verb. You can now talk about complex situations where you have to 'consider all the factors.' For example, when choosing a university, you consider the location, the cost, and the courses. This shows you can use the word to organize a logical argument. You might also use the phrase 'all things considered' to summarize a conversation. This level is about using 'consider' to connect different ideas and show that you are a balanced thinker who looks at both sides of a story.

B2 learners use 'consider' with much more nuance and variety. You understand the subtle difference between 'consider' and its synonyms like 'contemplate' or 'evaluate.' You might use 'consider' in more abstract ways, such as 'considering the implications of a new law.' You are also comfortable using it in various grammatical structures, including 'consider + wh- clauses' (e.g., 'We must consider whether the project is sustainable'). At this level, you use 'consider' to challenge ideas politely. 'Have you considered that the price might go up?' is a sophisticated way to point out a potential problem. You also recognize the use of 'consider' in literature and formal news reports. You can distinguish between 'considering' as a verb and 'considering' as a preposition (e.g., 'Considering his age, he runs very fast'). This flexibility allows you to handle more complex reading materials and participate in debates where you need to show you have thought deeply about the topic from multiple perspectives.

At the C1 level, 'consider' is a tool for precise and academic expression. You use it to define categories and establish status. 'This work is considered a masterpiece of modern art' or 'He is considered one of the leading experts in the field.' You are aware of the stylistic choice to omit 'as' or 'to be' to make your writing more punchy and professional. You also use 'consider' in the context of critical thinking, where you 'reconsider' your previous beliefs based on new evidence. This shows a high level of intellectual maturity. In professional writing, you might use 'consideration' as a noun in complex phrases like 'due consideration' or 'under consideration.' You understand the legal weight of the word in contracts and formal agreements. Your use of 'consider' is no longer just about making choices; it's about framing reality and social constructs. You can use it to discuss philosophical concepts, like 'considering the nature of reality,' and you can switch between formal and informal registers with ease, knowing exactly when 'consider' is too heavy or just right for the situation.

For C2 mastery, 'consider' is used with total command of its idiomatic and stylistic potential. You can use it to convey irony, sarcasm, or extreme politeness. You might use the phrase 'Consider it done' to show total confidence in completing a task. You understand the historical etymology—coming from the Latin 'considerare,' meaning to look closely at the stars—and how that sense of 'observation' still influences the word today. In high-level academic or legal discourse, you use 'consider' to navigate the finest points of deliberation. You might use it in the subjunctive or in complex conditional sentences. You are also a master of its related forms, like 'inconsiderable' (meaning small/unimportant) versus 'unconsidered' (meaning not thought about). Your usage is characterized by a perfect sense of collocations; you know exactly which adverbs (carefully, seriously, briefly, favorably) pair best with 'consider' in any given context. At this level, the word is not just a verb; it is a fundamental part of how you structure logical, persuasive, and nuanced communication in the English language.

Practice it Examples Notes & Tips

consider in 30 Seconds

To think carefully about something before making a decision.
To have a particular opinion or regard for someone or something.
To take into account specific facts or circumstances when judging.
A versatile verb used in both formal and informal English contexts.

The word consider is a versatile verb that describes the mental process of looking at something from different angles. At its core, it involves taking the time to think about a fact, a proposal, or a person's feelings before reaching a conclusion. It is not a fast thought; it is a purposeful one. Imagine you are standing at a crossroads in a forest. You don't just run down one path; you stop, look at the map, check the weather, and think about how tired you are. That entire process of stopping to think is what it means to consider your options.

Deliberation: This is the most common use. It refers to the time spent before making a choice. For example, 'I am considering buying a new car' means you are in the research and thinking phase.
Regard or Opinion: It can also mean how you view someone. 'I consider her my best friend' means that in your mind, she holds that specific status.

Please consider my application for the job; I have worked very hard to gain the necessary skills.

In social situations, 'considering others' is a sign of politeness and empathy. It means you are thinking about how your actions will affect the people around you. If you play loud music at night, you are not considering your neighbors. If you bring an umbrella for a friend because you saw it might rain, you are being very considerate. This word bridges the gap between pure logic and emotional intelligence, making it essential for both professional business meetings and personal relationships.

We must consider the environmental impact of this new factory before we start building.

Formal Evaluation: In legal or official contexts, a judge might 'consider the evidence,' which implies a deep, systematic review of facts to ensure justice is served.

You should consider yourself lucky that you didn't get hurt in the accident.

Using 'consider' correctly requires understanding its grammatical patterns. It is a transitive verb, meaning it usually takes an object. You consider *something* or *someone*. One of the most common structures is 'consider + noun phrase.' For example, 'They considered the proposal for three weeks.' Here, the proposal is the object of their thought. Another frequent pattern is 'consider + gerund (-ing).' You might say, 'I am considering changing my major.' This indicates a possible future action that is currently being weighed in your mind.

The 'As' Debate: When you want to say you view someone in a certain way, you can say 'I consider him a genius' or 'I consider him as a genius.' While both are used, the version without 'as' is generally preferred in modern, concise English.

The committee will consider all applications submitted before the deadline.

You can also use 'consider' followed by a 'wh-' clause, such as 'how,' 'whether,' or 'what.' For instance, 'We need to consider how this will affect our budget.' This is particularly useful in problem-solving scenarios. In more formal writing, you might see 'consider' used with an object and an infinitive: 'The court considered him to be innocent.' However, in daily speech, people usually shorten this to 'The court considered him innocent.' This flexibility makes 'consider' a powerful tool for expressing complex thoughts simply.

Have you considered taking a break? You look very tired.

Conditional Usage: 'If you consider...' is a great way to start a sentence when you want someone to look at a specific fact. 'If you consider the cost, it's actually a good deal.'

I consider it an honor to be invited to speak at your graduation.

'Consider' is a staple of professional and academic English, but it is equally common in domestic life. In a workplace, you will hear it during performance reviews: 'We are considering you for a promotion.' In a medical setting, a doctor might say, 'We need to consider all possible causes for your symptoms.' It implies a level of care and thoroughness that words like 'think' or 'guess' do not convey. When a professional says they are 'considering' something, they are signaling that they are taking the matter seriously and giving it the attention it deserves.

In Media and News: News anchors often use it when discussing government policy: 'The Senate is considering a new bill on climate change.' It suggests the bill is being debated and analyzed.

The director is considering several actors for the lead role in the upcoming movie.

In everyday conversation, you'll hear it when friends give advice. 'You should consider talking to him before you get angry.' It's a softer, more polite way of giving a suggestion than saying 'You must talk to him.' By using 'consider,' the speaker is giving the listener the power to make the final choice. You also hear it in the phrase 'all things considered,' which people use when they are summarizing a situation after looking at both the good and the bad parts. For example, 'The trip was rainy, but all things considered, we had a great time.'

When considering a new job, don't just look at the salary; look at the benefits too.

Academic Contexts: In essays, students are often asked to 'consider the following arguments,' which means they must analyze and critique them deeply.

Scientists consider this discovery to be the most important of the decade.

One of the most frequent errors learners make is using the wrong verb form after 'consider.' Many people naturally want to use the infinitive (to + verb) because other verbs like 'want' or 'hope' use it. However, 'consider' must be followed by a gerund. Saying 'I am considering to buy a house' is grammatically incorrect; the correct form is 'I am considering buying a house.' This is a high-frequency mistake that can make your English sound less natural, so it is worth memorizing this specific rule early on.

Confusing 'Consider' with 'Think': While they are similar, 'think' is often followed by 'about.' You 'think about' something, but you usually just 'consider' something. Saying 'I am considering about it' is redundant and incorrect.

Wrong: I consider to go.
Right: I am considering going.

Another mistake involves the use of 'as.' As mentioned before, 'I consider him as my friend' is acceptable but often seen as clunky. The more sophisticated way is 'I consider him my friend.' Furthermore, learners sometimes confuse 'consider' with 'regard.' While they are synonyms, 'regard' almost always requires 'as' (e.g., 'I regard him as a friend'), whereas 'consider' does not. Mixing these two patterns is a common source of confusion for intermediate students.

Wrong: She considers about the problem.
Right: She is considering the problem.

The Passive Voice Trap: When using the passive voice, don't forget the 'to be' verb. 'He considered a hero' is wrong; it must be 'He is considered a hero.'

It is widely considered the best restaurant in the city.

To truly master 'consider,' you should know when to use its synonyms to add variety to your speech. 'Think about' is the most common informal alternative. If you want to sound more formal or indicate a deeper level of thought, you might use 'contemplate' or 'ponder.' 'Contemplate' often implies looking at something for a long time, while 'ponder' suggests a quiet, almost philosophical reflection. In a business context, you might 'evaluate' or 'assess' a situation, which implies a more data-driven and objective type of considering.

Consider vs. Contemplate: 'Consider' is for general decision-making. 'Contemplate' is more intense and often used for life-changing decisions, like 'contemplating marriage.'
Consider vs. Deem: 'Deem' is very formal and usually used in legal settings. 'The judge deemed the evidence inadmissible' means the judge officially considered it and made a ruling.

Instead of just considering the price, you should also evaluate the quality.

Another useful alternative is 'weigh.' This is a metaphor for putting two options on a scale to see which is heavier or more important. 'I am weighing my options' is a very common idiomatic way to say you are considering different choices. If you are thinking about something very quickly or briefly, you might use 'glance at' or 'look over,' though these are much less deep than 'consider.' Understanding these nuances allows you to choose the exact word that fits the intensity of your thought process.

We need to ponder the long-term consequences of our current lifestyle.

Reflect on: This is used when thinking about the past. 'He reflected on his mistakes' means he considered them to learn a lesson.

The manager will review the data before making a final decision.

How Formal Is It?

Formal

Neutral

Informal

Child friendly

Slang

Fun Fact

Ancient Roman priests used to 'consider' the stars to predict the future, which is why the word implies such deep and careful looking.

Pronunciation Guide

UK /kənˈsɪd.ər/

US /kənˈsɪd.ɚ/

con-SID-er

Rhymes With

bewilder builder guilder reconsider bidder slider divider provider

Common Errors

Stressing the first syllable (CON-sid-er) is incorrect.
Pronouncing the 'o' as a strong 'O' instead of a schwa.
Forgetting the 'n' sound in the first syllable.
Making the 'i' sound like an 'ee'.
Dropping the final 'r' too abruptly in US English.

Difficulty Rating

Reading 2/5

Common in all types of text.

Writing 3/5

Requires knowledge of the -ing rule.

Speaking 2/5

Easy to pronounce but requires context.

Listening 2/5

Clear pronunciation in most dialects.

What to Learn Next

Prerequisites

think plan choice about good

Learn Next

contemplate evaluate decide option opinion

Advanced

deliberation speculation assessment scrutiny mediation

Grammar to Know

Gerunds vs Infinitives

I consider moving (Correct) vs I consider to move (Incorrect).

Passive Voice

He is considered a hero by many.

Reflexive Pronouns

She considers herself lucky.

Adverb Placement

We must carefully consider the facts.

Wh- Clauses

They are considering what to do next.

Examples by Level

I consider my cat my best friend.

Je considère mon chat comme mon meilleur ami.

Subject + consider + object + noun.

Please consider this gift.

S'il vous plaît, acceptez ce cadeau (pensez-y).

Imperative use of consider.

I am considering a new car.

Je réfléchis à une nouvelle voiture.

Present continuous for a current thought.

Consider the weather before you go out.

Pensez à la météo avant de sortir.

Consider + noun phrase.

They consider him a good teacher.

Ils le considèrent comme un bon professeur.

No 'as' is needed here.

We consider the price too high.

Nous trouvons le prix trop élevé.

Consider + object + adjective.

Do you consider me a friend?

Me considères-tu comme un ami ?

Question form.

I consider going to bed early.

Je pense à me coucher tôt.

Consider + gerund (-ing).

She is considering moving to London.

Elle envisage de déménager à Londres.

Gerund after consider.

It is considered rude to talk loudly here.

Il est considéré comme impoli de parler fort ici.

Passive voice: 'is considered'.

You should consider your health.

Tu devrais penser à ta santé.

Modal 'should' + consider.

We are considering all the options.

Nous étudions toutes les options.

Plural subject with present continuous.

He considers himself very lucky.

Il se considère très chanceux.

Reflexive pronoun 'himself'.

Consider taking the bus instead of driving.

Pense à prendre le bus plutôt que de conduire.

Gerund phrase as object.

They didn't consider the cost of the trip.

Ils n'ont pas tenu compte du coût du voyage.

Negative past simple.

Is he being considered for the job?

Est-il envisagé pour le poste ?

Passive continuous question.

All things considered, it was a success.

Tout bien considéré, ce fut un succès.

Fixed idiomatic phrase.

We need to consider how to solve this.

Nous devons réfléchir à la manière de résoudre cela.

Consider + wh- clause.

I consider it my duty to help you.

Je considère qu'il est de mon devoir de vous aider.

Consider + it + complement.

The manager is considering your request.

Le directeur examine votre demande.

Formal business context.

Have you considered the consequences?

As-tu pensé aux conséquences ?

Present perfect for life impact.

She is widely considered the best in her field.

Elle est largement considérée comme la meilleure dans son domaine.

Adverb 'widely' modifying the passive.

I'll consider what you said.

Je réfléchirai à ce que tu as dit.

Future simple for a promise to think.

We must consider the feelings of others.

Nous devons tenir compte des sentiments des autres.

Moral obligation with 'must'.

The proposal is still under consideration.

La proposition est toujours à l'étude.

Noun form in a prepositional phrase.

Considering the price, the quality is poor.

Compte tenu du prix, la qualité est médiocre.

Considering as a preposition.

He is considered to be the father of modern physics.

Il est considéré comme le père de la physique moderne.

Passive + infinitive 'to be'.

We are considering whether to expand the business.

Nous examinons s'il convient de développer l'entreprise.

Consider + whether + infinitive.

You must consider the impact on the environment.

Vous devez tenir compte de l'impact sur l'environnement.

Environmental context.

The court will consider the evidence tomorrow.

Le tribunal examinera les preuves demain.

Legal context.

I consider myself fortunate to have met you.

Je m'estime heureux de vous avoir rencontré.

Reflexive + adjective complement.

They are considering a variety of different approaches.

Ils envisagent diverses approches.

Consider + complex noun phrase.

The judge will take your age into consideration.

Le juge tiendra compte de votre âge.

Phrase: 'take into consideration'.

Reconsidering your position might be wise.

Il serait peut-être sage de reconsidérer votre position.

Gerund as a subject.

The findings are considered highly significant.

Les résultats sont considérés comme très significatifs.

Passive + adverb + adjective.

We must consider the ethical implications.

Nous devons examiner les implications éthiques.

Abstract noun object.

He was considered for the Nobel Prize.

Il a été pressenti pour le prix Nobel.

Passive past simple.

The area is considered a high-risk zone.

La zone est considérée comme une zone à haut risque.

Defining status.

I've been considering the matter deeply.

J'ai mûrement réfléchi à la question.

Present perfect continuous for duration.

Failure to consider these factors led to the crash.

Le fait de ne pas tenir compte de ces facteurs a conduit à l'accident.

Infinitive as part of a noun phrase.

Consider it done, sir.

Considérez que c'est fait, monsieur.

Idiomatic expression of certainty.

The sum involved is not inconsiderable.

La somme en jeu n'est pas négligeable.

Litotes using 'inconsiderable'.

His contribution was unconsidered by the board.

Sa contribution n'a pas été prise en compte par le conseil.

Adjective 'unconsidered' as passive participle.

One must consider the historical context of the era.

Il faut tenir compte du contexte historique de l'époque.

Formal 'one' as subject.

The plan was considered in light of recent events.

Le plan a été examiné à la lumière des événements récents.

Phrase: 'in light of'.

He is widely considered to have been the architect of the coup.

Il est largement considéré comme l'instigateur du coup d'État.

Perfect infinitive 'to have been'.

Without due consideration, the project will fail.

Sans un examen attentif, le projet échouera.

Formal noun usage 'due consideration'.

They considered themselves above the law.

Ils se considéraient au-dessus des lois.

Reflexive + prepositional phrase.

Synonyms

think about contemplate ponder reflect on weigh examine

Antonyms

ignore neglect disregard

Common Collocations

consider carefully

seriously consider

consider a possibility

fully consider

consider the impact

favorably consider

briefly consider

consider an option

consider the consequences

widely considered

Common Phrases

All things considered

— Taking everything into account.

All things considered, the party was a success.

Under consideration

— Being thought about or discussed.

Your request is currently under consideration.

Take into consideration

— To include a fact when making a decision.

Please take my travel time into consideration.

Consider it done

— A promise that a task will be completed immediately.

You need this by five? Consider it done!

Consider yourself lucky

— You should be happy because a bad thing didn't happen.

Consider yourself lucky you weren't in the car.

In light of (considering)

— Because of new information.

In light of the news, we must consider a new plan.

Consider the source

— Don't believe someone because they are not reliable.

He said I'm lazy? Well, consider the source.

Further consideration

— More thinking needed later.

After further consideration, I've decided to stay.

Give consideration to

— To think about something.

We gave serious consideration to your idea.

Out of consideration for

— Because you care about someone's feelings.

We stayed quiet out of consideration for the baby.

Often Confused With

consider vs think about

Think about is more informal and common in speech.

consider vs regard

Regard usually requires 'as', while consider does not.

consider vs believe

Believe is about faith; consider is about a mental process.

Idioms & Expressions

"Food for thought"

— Something worth considering.

That documentary gave me a lot of food for thought.

informal

"Sleep on it"

— To wait until the next day to make a decision.

Don't decide now; sleep on it and tell me tomorrow.

informal

"Mull it over"

— To think about something for a long time.

I need a few days to mull over the contract.

neutral

"Chew on that"

— Think about this interesting fact.

He's actually the boss's son. Chew on that for a while.

informal

"Take a step back"

— To stop and consider the whole situation objectively.

We need to take a step back and consider our goals.

neutral

"Look before you leap"

— Consider the risks before acting.

Buying a house is a big step; look before you leap.

informal

"Second thoughts"

— Doubts after considering something again.

I'm having second thoughts about moving to Alaska.

neutral

"On second thought"

— A phrase used when you change your mind.

I'll have the tea. On second thought, make it a coffee.

informal

"Weighty matter"

— A very serious thing to consider.

Choosing a president is a weighty matter.

formal

"In the back of one's mind"

— Considering something without focusing on it.

I had that problem in the back of my mind all day.

neutral

Easily Confused

consider vs considerable

Looks like the verb.

It means 'large' or 'significant', not 'thoughtful'.

A considerable amount of money.

consider vs considerate

Related root.

It is an adjective meaning 'kind' or 'thoughtful of others'.

He is a very considerate neighbor.

consider vs considering

Verb vs Preposition.

As a preposition, it means 'taking into account'.

Considering the rain, we stayed inside.

consider vs consignment

Similar start.

A business term for sending goods.

The goods were sent on consignment.

consider vs consistent

Similar start.

Means 'always acting or behaving in the same way'.

Her work is very consistent.

Sentence Patterns

I consider + noun

I consider the cake.

I am considering + gerund

I am considering eating.

It is considered + adjective

It is considered nice.

Consider + whether

Consider whether to go.

Take + noun + into consideration

Take his age into consideration.

Consider + object + to have been

He is considered to have been first.

All

All things considered

All things considered, it was good.

All

Consider + object + noun

I consider him a friend.

Word Family

Nouns

Verbs

Adjectives

How to Use It

frequency

Very high; used daily in speech and writing.

Common Mistakes

I consider to move. → I am considering moving.
You must use a gerund (-ing) after consider.
I consider about it. → I am considering it.
Do not use 'about' with consider; it is not like the verb 'think'.
He is consider a hero. → He is considered a hero.
In the passive voice, you need the past participle 'considered'.
I consider him as my brother. → I consider him my brother.
While 'as' is used, it is more natural to omit it.
The cost is inconsiderate. → The cost is inconsiderable.
Inconsiderate is for people's feelings; inconsiderable is for small amounts.

Tips

The -ing Rule

Always follow 'consider' with a gerund (-ing) when using another verb. This is the #1 mistake learners make.

Drop the 'As'

For more professional writing, remove 'as' when using consider to define something. 'I consider it a success' sounds better.

Use 'Considerate'

If you want to describe a person who thinks of others, use the adjective 'considerate'.

Polite No

Use 'I'll consider it' if you want to be polite but aren't ready to say 'yes' yet.

Essay Hook

Start a paragraph with 'Considering the evidence...' to sound more academic.

Schwa Sound

The first 'o' is very weak. It sounds like 'kuhn', not 'kon'.

Food for Thought

Use this phrase when someone tells you something that makes you 'consider' new ideas.

Under Consideration

Use this phrase in emails to tell someone you are still thinking about their request.

Empathy

To 'consider others' is a great way to describe being a kind person in English.

Star Gazer

Remember the Latin root 'sid' (star). Imagine you are looking at stars to make a choice.

Memorize It

Mnemonic

CON-SID-ER: 'CON' (with) 'SID' (sit) 'ER'. Imagine sitting with an idea for a long time.

Visual Association

Imagine a person sitting on a bench, looking at two different paths, holding a magnifying glass.

Word Web

Think Judge Plan Choice Mind View Study Review

Challenge

Try to use 'consider' three times today instead of 'think about' when talking to friends.

Word Origin

From the Latin 'considerare', which means 'to examine' or 'to observe'.

Original meaning: Literally 'to observe the stars' (con- + sidus/sideris 'star').

Italic -> Latin -> Old French -> Middle English.

Cultural Context

Be careful using 'I'll consider it' if you actually mean 'No', as it can be seen as misleading in very direct cultures.

It is a key word in 'polite' or 'indirect' English speech.

'Consider the lilies of the field' (Bible) 'Consider yourself one of the family' (Oliver!) The Thinker (Rodin statue)

Practice in Real Life

Real-World Contexts

Shopping

Consider the price
Consider the size
Consider the brand
Consider the quality

Work

Consider a promotion
Consider a deadline
Consider a strategy
Consider a colleague

Travel

Consider the route
Consider the cost
Consider the weather
Consider the time

Relationships

Consider feelings
Consider the future
Consider advice
Consider a gift

School

Consider the question
Consider the facts
Consider the answer
Consider the grade

Conversation Starters

"Have you ever considered moving to another country?"

"What do you consider to be the most important quality in a friend?"

"Are you considering taking any new classes this year?"

"What should I consider before buying a new laptop?"

"Do you consider yourself a morning person or a night owl?"

Journal Prompts

Write about a big decision you are currently considering.

Who do you consider to be your biggest role model and why?

Consider how your life has changed in the last five years.

What factors do you consider when you are choosing a new book to read?

Consider a time when you made a choice without thinking. What happened?

Frequently Asked Questions

10 questions

No, you must use the -ing form: 'consider going'. This is a very common rule for this verb.

It is not strictly wrong, but it is less natural. 'I consider him a friend' is better than 'I consider him as a friend'.

It means 'after thinking about all the facts'. It is used to give a final summary of a situation.

It is neutral. It works perfectly in both a casual chat and a business meeting.

The most common noun is 'consideration'.

Yes, you can consider someone for a job or consider someone a friend.

Sometimes, but 'consider' implies you have thought about it, while 'believe' can be just a feeling.

It is an opinion that you have thought about very carefully, not a quick guess.

Put the thing you are thinking about in the middle: 'Take the cost into consideration'.

The best opposites are 'ignore' or 'disregard'.