Adj / Adv / Verb / Noun A2 – Upper Elementary /fɑːst/

Fast — Definition, Examples & Pronunciation

Moving quickly, happening in a short time — or choosing to go without food. One small word with four grammatical lives.

Quick Definitions

Adjective: Moving quickly; happening or completed in a short time. “She is a fast learner.”

Adverb: At high speed; quickly. “He ran as fast as he could.”

Verb: To go without eating food, usually for religious or health reasons. “She fasts every Monday.”

Noun: A period of time during which a person goes without eating. “He broke his fast at dawn.”

What Does Fast Mean?

Fast is one of the most versatile words in English. It can serve as an adjective, adverb, verb, or noun — yet in everyday conversation it most commonly describes speed. When learners first encounter the verb and noun senses (related to not eating), they are often surprised that the same spelling carries such a different meaning.

As an adjective, fast describes something or someone moving at great speed or completing an action in a short time: a fast train, a fast worker. As an adverb it modifies a verb without changing its form: drive fast, think fast. Crucially, there is no form fastly — fast is already the adverb, or you may use quickly instead.

The verb to fast means to abstain from food deliberately, often for religious observance (Ramadan, Yom Kippur, Lent) or for health purposes such as intermittent fasting. The related noun a fast names the period itself. The phrase break one’s fast is the origin of the word breakfast — the meal that ends the night’s fast.

Etymology

Word History

Fast descends from Old English fǦst meaning “firm” or “fixed in place”. The sense of “moving quickly” emerged around the 13th century, likely because something spinning rapidly on a fixed axis (such as a wheel) appears to move swiftly. The verb meaning “to abstain from food” comes from Old English faestan, meaning “to hold firm” — that is, to hold firm against the temptation to eat. Both strands share the same Germanic root, which also appears in German fest (firm, solid) and Dutch vast (fixed). The expression hold fast, used in sailing to mean “grip the rope tightly”, preserves the oldest sense. The word breakfast literally means to break one’s overnight fast.

Example Sentences by CEFR Level

LevelSentenceUsage note
A2My dog is very fast — he can run faster than any other dog in the park.adjective; comparative faster
B1She is a fast learner — she mastered the grammar quickly.fast modifying a noun
B1The city’s population has been growing fast over the past decade.fast as adverb after a verb
B2Many people choose to fast for 16 hours a day as part of an intermittent fasting routine.fast as verb; compound noun
C1Technological change is advancing at such a fast pace that regulators struggle to keep up; industries that fail to adapt risk becoming obsolete.fast pace; complex clause structure

Collocations

CollocationGrammarExample
fast caradjective + nounHe always dreamed of owning a fast car.
fast foodcompound nounFast food restaurants are found in every city.
fast learneradjective + nounOur new colleague is a fast learner.
fast paceadjective + nounThe fast pace of modern life can be stressful.
fast-pacedcompound adjectiveIt is a fast-paced thriller that keeps you reading.
run fastverb + adverbYou need to run fast to catch the bus.
think fastverb + adverbIn a crisis, you have to think fast.
break a fastverb + nounShe broke her fast with dates and water.
hold fastverb + adverb (idiomatic)Hold fast to your principles, no matter what.
fast asleepadverb + adjective (fixed)The baby was fast asleep in five minutes.

Usage Notes

How to Use Fast Correctly

  • No “fastly”: Unlike most adjectives, fast does not add -ly to form an adverb. The adverb form is simply fast. Use quickly if you prefer a form ending in -ly.
  • Fast vs. quickly: Both can mean “at speed”, but fast tends to emphasise continuous high speed (drive fast), while quickly is more natural for brief actions (finish quickly, answer quickly).
  • Fast vs. quick before a noun: Before a noun, quick is more common in everyday British English (a quick decision), though fast is also correct (a fast decision). In formal or technical contexts, rapid is often preferred.
  • Fast (verb) takes no direct object: You can say I am fasting or I am fasting for 24 hours. Do not say I am fasting food — use abstaining from food instead.
  • Fast asleep is fixed: This phrase uses an archaic adverb sense of fast meaning “firmly, deeply”. It cannot be replaced with quickly asleep or rapidly asleep.

Common Mistakes

Watch Out For

She drives fastly on the motorway.

She drives fast on the motorway. (fast is already the adverb; fastly does not exist)

He is more fast than his brother.

He is faster than his brother. (use the inflected comparative faster, not more fast)

I am fasting food for health reasons.

I am fasting for health reasons. (the verb fast takes no direct object)

The children fell quickly asleep after the story.

The children fell fast asleep after the story. (fast asleep is a fixed phrase; quickly cannot replace fast here)

Synonyms & Antonyms

quick rapid swift speedy brisk hasty fleet slow sluggish leisurely unhurried gradual

Related Words

faster fastest fasting fast-paced breakfast ability All Common Words → Grammar Glossary

Practise This Word

Flash Cards Complete the Sentence Vocabulary Quiz Hangman

Frequently Asked Questions about “fast”

What does fast mean in English?
Fast has four grammatical roles in English. As an adjective it means moving quickly or happening in a short time: “a fast car”. As an adverb it means quickly: “She runs fast.” As a verb it means to go without eating food: “Many people fast during religious holidays.” As a noun it refers to a period of not eating: “She broke her fast at sunrise.” The adjective and adverb forms are identical in spelling, which often surprises learners.
What is the difference between fast and quick?
Both fast and quick describe speed, but they are used differently. Fast typically describes continuous movement or a steady high speed: “a fast train”, “she runs fast”. Quick more often describes something done in a short time or without delay: “a quick answer”, “have a quick look”. Fast is less commonly used before a noun in formal writing, while quick is common in that position. Quick also has the adverb form quickly, whereas fast is its own adverb.
How do you use fast as an adverb?
As an adverb, fast follows the verb it modifies and does not change its form: “He drives fast”, “She learned fast”, “Time passes fast”. Do not use “fastly” — it does not exist in standard English. The correct adverb is simply fast, or you may use quickly as an alternative.
What is the verb to fast?
The verb to fast means to deliberately go without eating food, usually for religious, medical, or health reasons. Example: “Muslims fast during the month of Ramadan.” The past tense is fasted: “He fasted for 24 hours before his blood test.” The noun derived from this verb is a fast: “a 16-hour fast”.
What does hold fast mean?
Hold fast is an idiomatic expression meaning to hold on tightly or to remain firm in a belief or position. Example: “Hold fast to your dreams.” It comes from nautical language, where sailors would call “hold fast” to signal that ropes must be gripped firmly. Today it is used figuratively to mean persisting in the face of difficulty.
What are common collocations with fast?
Common collocations with fast as an adjective include: fast car, fast food, fast learner, fast pace, fast internet. Common collocations with fast as an adverb include: run fast, drive fast, think fast, talk fast, grow fast. Common collocations with the verb to fast include: fast for 24 hours, fast during Ramadan, fast before surgery, break a fast, intermittent fasting.
What is the comparative form of fast?
The comparative form of fast is faster and the superlative is fastest. Example: “This computer is faster than my old one.” “She is the fastest runner in the school.” In informal speech, more fast is sometimes heard but faster is always the standard and preferred form in British English.
What does fast asleep mean?
Fast asleep is a fixed phrase meaning in a deep, sound sleep. Here fast is an archaic adverb meaning firmly or deeply. Example: “The children were fast asleep before 9 o’clock.” You cannot use quickly in this expression — it is only correct with the specific adverb fast.
What is the origin of the word fast?
The word fast comes from Old English faest, meaning “firm” or “fixed”. The sense of “quick” developed in the 13th century, probably because something fixed in place (like a wheel spinning on an axle) moves rapidly. The verb meaning “to go without food” comes from Old English faestan, meaning “to hold firm” against the temptation to eat. Both meanings share the same Germanic root, which also gives us German fest (firm) and the word breakfast (literally: break one’s fast).
How can I practise using fast in English?
Try LexFizz’s Complete the Sentence exercise to practise fast in context, or use the Flash Cards tool to test vocabulary including fast and its related forms (faster, fastest, fasting, fast-paced). Focus especially on the four different parts of speech — adjective, adverb, verb, and noun — as confusing them is a common learner error.