What does fast mean?
Fast is one of English's most versatile words, serving as an adjective, adverb, verb, and noun. Most familiarly, it describes speed: a fast runner, a fast train, or an adverbial instruction like 'drive fast'. Less obviously, it can mean firmly fixed or secure — 'hold fast' and 'stuck fast' use this older sense, where fast implies immobility rather than velocity. As a verb and noun, fast refers to deliberately going without food for a set period, a practice central to many religions, including Islam's Ramadan and Christianity's Lent, and popular in modern health culture. This striking split between 'quick' and 'fixed' traces back to Old English, where the word originally emphasized steadfastness, with the speed sense developing later. Fast appears constantly in everyday language through phrases such as 'fast asleep' and 'fast food'. Its range, history, and frequency make it an essential word for any vocabulary.
Moving, happening, or able to operate quickly; also, firmly fixed or secure.
"That is the fastest route to the airport."
When applied to clocks ('a fast clock'), it means showing time ahead of the correct time.
Quickly; at high speed.
"News of the merger spread fast."
To abstain from all or some kinds of food and drink, especially as a religious observance or for health reasons.
"Devout observers fast during daylight hours throughout Ramadan."
A period of deliberate abstention from food and drink.
"He undertook a three-day fast before the medical procedure."
Applies when counting multiple periods of fasting; the plural refers to distinct instances or observances rather than a single continuous fast.
"Religious calendars may prescribe several fasts throughout the year."
The same Old English word that gave us 'fast car' also meant 'firmly fixed' — which is why you can be 'stuck fast', the exact opposite of moving at all.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fast
Fast comes from the Old English adjective 'fæst', meaning firm, secure, or steadfast — its original sense was about being fixed in place, not about speed. It shares roots with related Germanic words, including the verb 'fasten', formed from the same base. The sense of rapid movement developed later in Middle English, likely influenced by the idea of running 'fast' (firmly) forward. The religious practice of fasting gives the word its verb and noun forms, drawing on the notion of holding firmly to a discipline or resolve.
Related word forms
How fast is actually used
The two core meanings — quick and firm — pull in opposite directions and often surprise learners: 'stuck fast' means unable to move, while 'running fast' means rapid movement. The religious sense of fasting carries a solemn, formal register, while 'fast' describing speed is neutral and extremely common.
Easily confused with fast
'Fast' means quick or to abstain from food, while 'fasten' is a separate verb meaning to attach or secure something.