fault

fault — noun

1. the state of being the person who caused a problem or made an error.

1.nounA2
Definition

the state of being the person who caused a problem or made an error.

Example

The car crash was entirely Christopher's fault because he ran a red light.

be + possessive + fault — assigning responsibility

It is not the teacher's fault that the students did not prepare for the exam.

it is + possessive + fault + that-clause

Common collocations
  • admit fault
  • share fault
  • sb's fault
  • at fault
Synonyms
  • blame

    Focuses on who is held responsible rather than the condition of being responsible; 'the blame lies with me' vs 'it's my fault'.

  • responsibility

    More neutral and formal; can be positive or negative, while 'fault' is always negative.

  • guilt

    Stronger, implying moral or legal wrongdoing; more serious than 'fault'.

Antonyms
  • credit

    Recognition for something good, the opposite of blame or fault.

Usage Note

Often appears in fixed expressions: 'be someone's fault' (informal, daily speech) or 'be at fault' (slightly more formal). 'Admit fault' is a formal collocation used in legal or business contexts.

Common Mistakes

The mistake is my wrong.
The mistake is my fault.
'fault' is the noun for responsibility, not 'wrong'.
I made a fault.
I made a mistake.
'fault' as a count noun means a defect or character flaw, not a simple error. Use 'mistake' for everyday errors.

2. a part of someone's character that is seen as weak, bad, or not good enough.

2.nounB1
Definition

a part of someone's character that is seen as weak, bad, or not good enough.

Example

Jabari's only fault is that he trusts people far too easily.

possessive + only fault + is that-clause

Everyone has faults, but a good friend accepts you anyway.

Common collocations
  • sb's only fault
  • biggest fault
  • acknowledge faults
  • have faults
Synonyms
  • weakness

    Softer and more neutral than 'fault'; can also refer to non-moral traits.

  • defect

    More formal and severe; often used for character in literary contexts.

  • shortcoming

    Implies falling short of a standard; gentler than 'fault'.

Antonyms
  • virtue

    A morally good quality in someone's character.

  • strength

    A positive trait; the opposite of a weakness.

Common Mistakes

His fault is that he is short.
His fault is that he is impatient.
'fault' for character should be a moral or behavioural weakness, not a physical trait.

3. an imperfection in a machine, system, or design that keeps it from running corre

3.nounB1
Definition

an imperfection in a machine, system, or design that keeps it from running correctly.

Example

The engineers found a fault in the braking system of the new train.

fault in — followed by system/machine/design

A small fault in the software caused the entire website to shut down.

Common collocations
  • fault in
  • fault with
  • manufacturing fault
  • structural fault
  • design fault
Synonyms
  • defect

    Very close in meaning; 'defect' often implies a manufacturing or production issue, while 'fault' can also include design problems.

  • flaw

    Suggests a small or hidden imperfection; slightly less technical.

  • bug

    Specifically for software or computer systems; informal.

Usage Note

Often used with prepositions 'in' or 'with' (a fault in the design, a fault with the engine). For electronic devices, 'fault' is more technical than 'problem' or 'issue'.

Common Mistakes

This phone has a fault.' (too vague)
This phone has a fault in its charging port.
specify where the fault is using 'in'.

4. a serve in tennis or similar racket sports that is illegal because the ball land

4.nounB2
Definition

a serve in tennis or similar racket sports that is illegal because the ball lands outside the correct area of the court.

Example

Samir served two faults in a row and lost the game quickly.

The umpire called a fault when the ball hit the net.

call a fault — official calls the fault

Common collocations
  • serve a fault
  • call a fault
  • double fault
  • foot fault
Synonyms
  • double fault

    Two faults in a row, which loses the point — more specific than a single 'fault'.

  • foot fault

    A specific type of fault where the server steps on or over the baseline.

Antonyms
  • ace

    A legal serve that the opponent cannot touch.

Usage Note

Two consecutive faults (a 'double fault') means the server loses the point. In tennis scoring, a fault is not the same as a 'foot fault', which is a rule about foot placement during the serve.

5. used only in the fixed patterns 'be at fault' and 'be someone's fault' to show t

5.nounB1
Definition

used only in the fixed patterns 'be at fault' and 'be someone's fault' to show that a particular person is the cause of a problem, with no standalone noun use for this meaning.

Example

The delivery was late, but the warehouse was at fault, not the driver.

be at fault — fixed expression for responsibility

It was entirely Rania's fault that the meeting started late.

Common collocations
  • at fault
  • sb's fault
Synonyms
  • to blame

    Equivalent phrasing: 'the driver is to blame' = 'the driver is at fault'.

Grammar Patterns

be + at + fault

be + possessive + fault

Usage Note

This is an idiomatic sense that always appears in the fixed expressions 'be at fault' (more formal) or 'be someone's fault' (everyday speech). It is not a standalone noun sense — the noun always appears within these phrases.

Common Mistakes

I am fault for the delay.
I am at fault for the delay.
the preposition 'at' is required.
It is my wrong.
It is my fault.
'fault' not 'wrong' in this expression.

6. to keep pointing out what is wrong with someone or something, often in an unfair

6.nounB2
Definition

to keep pointing out what is wrong with someone or something, often in an unfair or overly critical way.

Example

Her supervisor was always finding fault with her reports, even when they were excellent.

find fault with + object — fixed expression

Maeve told her friend to stop finding fault with every detail of the party plan.

Common collocations
  • find fault with
Synonyms
  • criticize

    More general; does not carry the implication of unfairness that 'find fault with' does.

  • nitpick

    Informal; focuses on minor details.

Antonyms
  • praise

    To express approval — the opposite of finding fault.

Grammar Patterns

find + fault + with

Usage Note

Always used in the fixed expression 'find fault with'. The noun 'fault' does not vary — you cannot say 'find a fault with' in this idiomatic sense (that would mean locating a defect, which is sense 3).

Common Mistakes

He finds faults with everything I do.
He finds fault with everything I do.
the expression is always singular 'fault'.

7. a break in the planet's rocky outer layer that has split into two sections and s

7.nounB2
Definition

a break in the planet's rocky outer layer that has split into two sections and shifted in opposite directions.

Example

The San Andreas Fault is one of the most studied geological features in the world.

Earthquakes often happen along fault lines where tectonic plates meet.

fault line — the visible surface line of a fault

Common collocations
  • fault line
  • fault zone
  • geological fault
  • along a fault
  • fault system
Synonyms
  • fault line

    Refers specifically to the line on the surface where the fault can be seen.

  • fracture

    A more general term for any break in rock; less specific than 'fault'.

Usage Note

In geology, 'fault' is a technical term. A 'fault line' is the surface trace of a fault, while 'fault zone' refers to the broader area of fractured rock around the main fault.

Idioms

find fault (with somebody/something)

idiom

To keep noticing and criticizing small problems or mistakes in someone or something.

Sara's teacher always finds fault with her homework.

Why do you find fault with every suggestion I make?

to a fault

idiom

Having a good quality to an extreme degree that may be seen as a weakness.

Diego is honest to a fault, always telling the truth.

Maya is generous to a fault, giving away her lunch money.

fault — verb

Word family

  • faultless
    adjectiveB2
  • faulty
    adjectiveB1
  • faultily
    adverbC1
  • faultiness
    nounC1
  • fault-finding
    nounC1

Synonym discussion

Sense: noun/1

All four words relate to being accountable for something bad, but they differ in tone and range. 'Fault' (noun/1) focuses on who is the cause of a problem in everyday situations — it is the most conversational of the four, especially in expressions like 'it's my fault'. 'Blame' is about pointing a finger at someone: you 'assign blame' or 'place blame', but the word itself is an action as much as a state. 'Guilt' is heavier — it carries moral or legal weight. You feel guilty about a lie; you are found guilty in court. 'Responsibility' is neutral and can be positive: you take responsibility for a team win or a project failure. 'Fault' is always negative. For everyday errors, choose 'fault' ('It was an honest fault'). For a stronger, morally charged context, choose 'guilt' ('He admitted his guilt'). For formal or workplace settings, 'responsibility' or 'blame' work best depending on whether you are describing the condition or the accusation.

fault ↗blame ↗guilt ↗responsibility ↗

Common collocations

Nouns

Adverbs

Phrases

Prepositions

Etymology

LatinOld FrenchEnglish

The word 'fault' comes from Old French 'faute' (meaning a lack, failure, or deficiency), which in turn came from the Latin 'fallere' (to deceive, disappoint, or fail). In Latin, 'fallere' carried the sense of letting someone down or tripping them up. The word entered English around the 13th century, first meaning 'a lack' or 'a deficiency', and later expanding to include moral weakness, responsibility for error, and physical defects. The geological sense (a crack in the earth's crust) appeared in the late 1700s as mining and geology developed. The verb sense 'to find fault with someone' developed from the Old French legal term 'faute' meaning 'wrongdoing'.