reason

reason — noun

1. something that explains why a particular event, situation, or action happened, o

1.nounA1
Definition

something that explains why a particular event, situation, or action happened, or why someone behaves or feels a certain way.

Example

Obi gave his teacher a simple reason for being late: the bus broke down.

reason + for + noun phrase / -ing

The main reason why Wei moved to Taipei was the job offer at the hospital.

reason + why + clause

Common collocations
  • main reason
  • real reason
  • simple reason
  • reason for
  • reason why
Synonyms
  • cause

    focuses on what directly makes something happen; more scientific/neutral than 'reason'

  • motive

    a reason for doing something, especially one kept hidden or involving personal gain

  • explanation

    a statement that makes something clear; broader than 'reason'

Antonyms
  • result

    the outcome, rather than the cause or explanation

  • effect

    what happens because of something, not the reason why

Grammar Patterns

reason + for + noun/-ing

reason + why + clause

reason + that + clause

the reason...is that...

Usage Note

Followed by for (reason for something), why (reason why…), or a that-clause (the reason is that…). Unlike 'cause', 'reason' focuses on the explanation offered by a person rather than a direct physical cause.

Common Mistakes

The reason of the accident is still unknown.
The reason for the accident is still unknown.
use 'reason for', not 'reason of'.
The reason is because the train was delayed.
The reason is that the train was delayed.
'the reason is because' is considered redundant.

2. a formal phrase used in legal or official writing to mean 'because of' a particu

2.nounB2
Definition

a formal phrase used in legal or official writing to mean 'because of' a particular fact or situation.

Example

The defendant was found not guilty by reason of mental illness.

by reason of + noun phrase (formal/legal)

By reason of her age, Mrs. Chen was excused from jury duty.

Common collocations
  • by reason of
Synonyms
  • because of

    the everyday equivalent; much more common in speech and informal writing

  • due to

    semi-formal alternative, common in both written and spoken English

  • owing to

    slightly formal, often used to explain a positive or neutral outcome

Grammar Patterns

by reason of + noun phrase

Usage Note

Used almost exclusively in formal, legal, or official writing. In everyday conversation, use 'because of' or 'due to' instead.

Common Mistakes

By reason of the rain, we stayed inside.' (too formal for casual speech)
Because of the rain, we stayed inside.
reserve 'by reason of' for formal or legal contexts.

3. the ability that humans have to think clearly, use logic, form sensible opinions

3.nounB2
Definition

the ability that humans have to think clearly, use logic, form sensible opinions, and tell right from wrong.

Example

Beatriz used her reason to figure out which offer was the best deal.

uncountable, no article

Humans are unique among animals in their power of reason.

Common collocations
  • power of reason
  • use reason
  • without reason
  • lose one's reason
Synonyms
  • logic

    focuses on strict rules of reasoning; more technical than 'reason'

  • rationality

    the quality of being based on reason; more abstract and formal

  • sense

    practical, everyday good judgment; less formal than 'reason'

Antonyms
  • emotion

    feeling, as opposed to logical thinking

  • madness

    loss of mental capacity, the opposite of sound reason

Grammar Patterns

reason + verb

with/without reason

Usage Note

Uncountable and usually used without an article ('reason', not 'a reason'). Frequently appears in fixed expressions: 'lose one's reason', 'power of reason', 'without reason'. Distinguish from sense 1 ('a reason' = a specific explanation).

Common Mistakes

He used a reason to solve the problem.' (countable form)
He used reason to solve the problem.
this sense is uncountable; it means logical thinking ability, not a specific explanation.

4. within limits that most people would consider sensible, fair, and acceptable — n

4.nounB2
Definition

within limits that most people would consider sensible, fair, and acceptable — not going too far.

Example

You can spend whatever you like on the party, within reason.

fixed phrase at end of sentence

The landlord said we could decorate the apartment within reason.

Common collocations
  • within reason
Synonyms
  • sensibly

    adverb form; 'within reason' is a fixed phrase while 'sensibly' is a free adverb

  • moderately

    suggests staying within middle limits; slightly more formal

Antonyms

Grammar Patterns

within reason

Usage Note

Always appears as the fixed phrase 'within reason' after a statement of permission or possibility. Cannot be modified (*within reasonable). Often implies an unspoken limit that the speaker and listener both understand as sensible.

Common Mistakes

You can stay out late within reasonable.
You can stay out late within reason.
the fixed form is always 'within reason', not 'within reasonable'.
Idioms

stand to reason

idiom

to be obviously true or logical based on the facts that everyone already knows.

It stands to reason that if you practice every day, your skills will improve.

It stands to reason that Ingrid got the promotion — she had the most experience.

rhyme or reason

idiom

any sensible explanation, order, or purpose — almost always used in negative sentences to say something makes no sense at all.

There was no rhyme or reason to the way the files were organized.

The rules changed every week without rhyme or reason, confusing everyone.

it stands to reason

idiom

It is logical or obvious to anyone who thinks about it.

It stands to reason that Sara will win the race.

If you don't study, it stands to reason you'll fail.

reason — verb

Word family

Synonym discussion

Sense: noun/1

These three words all relate to why something happens, but they differ in focus. 'Reason' is the broadest — it is the explanation a person gives or finds for an event, action, or feeling ('She had a good reason for leaving early'). 'Cause' is more direct and factual; it points to what makes something happen in a physical or scientific sense ('The cause of the fire was a faulty wire'). 'Motive' is narrower and more personal — it refers to a hidden or internal reason for doing something, often involving self-interest ('The police searched for a motive in the murder case'). 'Explanation' is the most general term for a statement that makes something clear, and it can cover both reasons and causes. In everyday conversation, 'reason' is the safest choice; use 'cause' for scientific or factual events, 'motive' for personal intentions, and 'explanation' when you are describing a process rather than justifying it.

cause ↗motive ↗explanation ↗

Common collocations

Prepositions

Etymology

LatinFrenchEnglish

'Reason' comes from Old French 'raison', which came from Latin 'rationem' (meaning 'a reckoning, understanding, or logical faculty'). The Latin root 'ratus' means 'thought out, calculated' — a past participle of 'rerī' (to think or reckon). The word entered English in the 13th century, first referring to the mental faculty of logical thinking, and later developed the sense of 'a cause or explanation' in the 14th century.