What does fail mean?
Fail is one of English's most fundamental verbs, meaning to be unsuccessful in achieving a goal, meeting a standard, or performing as expected — whether in an exam, a business venture, a machine, or one's own body. It also carries a second core sense of neglecting or omitting to do something, as in "she failed to mention the deadline." The word is neutral in register and appears across formal writing and everyday speech alike, though its noun form ("an epic fail") leans distinctly informal and humorous. Common collocations include "fail an exam," "fail to do something," and "without fail," meaning unfailingly or every single time. Derived forms include failure, failing, and failed. Fail traces back through Old French faillir to Latin fallere, "to deceive" or "to disappoint," which also gives us fault and default. Few words capture both human effort and its limits so concisely.
To be unsuccessful in achieving a goal, passing a test, or meeting a required standard.
"He failed his driving test on his first attempt."
To neglect or omit to do something expected or required.
"The company failed to deliver the order on time."
An instance of failing, or informally, a person or thing that is unsuccessful.
"The product launch was an embarrassing fail."
Informal; often humorous or mocking in tone.
Used chiefly in informal contexts to mean instances of failure or unsuccessful attempts.
"Despite several early fails, the startup eventually found its footing."
The word "fail" comes from Latin *fallere*, "to deceive" — so when something fails you, it has, quite literally, let you down.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fail
Fail entered Middle English from Old French faillir, itself derived from Latin fallere, meaning "to deceive, disappoint, or slip away." The same Latin root produced English words such as fault, default, and failure. The verb has carried its sense of being unsuccessful since at least the medieval period.
Related word forms
How fail is actually used
"Fail" is common in both formal and informal registers. In the sense of neglecting to act, it typically takes an infinitive complement ("fail to arrive"). As a noun, especially in informal American English ("an epic fail"), it carries a playful or mocking tone. The phrase "without fail" means reliably and invariably.
Easily confused with fail
"Flail" means to wave or thrash about wildly, while "fail" means to be unsuccessful; they differ by one letter but are unrelated in meaning.