Fault vs That was a mistake

When to use each in English, with meaning, register, and examples.

Fault

Top 1,000 (very common)B2noun

That was a mistake

Top 5,000 (fairly common)
Most common: Fault
 FaultThat was a mistake
Pronunciation🇬🇧 /["/fɔːlt/"]/🇺🇸 /["/fɔːlt/"]/🇬🇧 //ðæt wəz ə mɪˈsteɪk//🇺🇸 //ðæt wəz ə mɪˈsteɪk//
MeaningA mistake or a problem in something.An error or something wrong that was done.
ExampleThe engineer quickly identified the fault in the electricity supply.When I missed the deadline, I knew that was a mistake.
RegisterNeutralNeutral
How commonTop 1,000 (very common)Top 5,000 (fairly common)
CEFR levelB2-
Part of speechnoun
Collocationsstupid, entire, lie with somebody, at fault, through somebody’s fault, without fault, be all somebody’s fault, be entirely somebody’s fault, be largely somebody’s fault, big, great, moral, have, be blind to, overlook, fault in, for all somebody’s faults, to a fault, major, minor, dangerous, have, develop, look for, occur, lie in something, fault in, fault with, for all its faults, double, foot, serve, earthquake, geological, line, scarp, systemmake a mistake, admit a mistake, correct a mistake
Antonymsmerit, virtue, advantage-
Common mistakesConfusing 'fault' with 'error' — 'fault' often implies blame., Using 'fault' inappropriately as a verb instead of a noun., Misplacing the article — 'the fault' vs. 'fault'.Using past tense incorrectly, e.g., saying 'That is a mistake' when referring to a past action., Omitting the subject, leading to phrases like 'Was a mistake.', Confusing it with other expressions like 'That was wrong.'
Usage notesUse 'fault' in both formal and informal conversations when discussing blame or a defect. Avoid using it in overly casual contexts."That was a mistake" is often used to acknowledge an error. It's suitable for casual and formal conversations but may be less appropriate in very light-hearted contexts.

See it in real clips

Fault
That was a mistake

Frequently asked questions: Fault vs That was a mistake

What's the difference between Fault and That was a mistake?

Fault: A mistake or a problem in something. That was a mistake: An error or something wrong that was done.

Which is more common: Fault and That was a mistake?

Fault is the most common in everyday English.

Can you show an example of each?

Fault: The engineer quickly identified the fault in the electricity supply. That was a mistake: When I missed the deadline, I knew that was a mistake.

Can I use Fault and That was a mistake interchangeably?

Not always. Fault and That was a mistake are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.

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