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"Fast" describes continuous high speed; "quick" describes brevity or a short burst of speed.
Side-by-side comparison
"Fast" describes a high speed in a sustained or general way. "A fast car" = a car that goes at high speed. It can be both adjective and adverb.
She is a very fast runner, she won every race this season.
The train travels fast, reaching 300 km/h on this route.
Time passes fast when you are having fun.
"Quick" emphasizes the shortness of time something takes or the speed of a reaction. "A quick look" = a brief glance. "Quick thinking" = reacting with speed.
Can I ask you a quick question? It will not take long.
Let us have a quick meeting before the presentation.
She is a quick learner, she picked it up in two days.
Common mistake
"He is a quickly driver" is wrong: "quickly" is an adverb and cannot modify a noun. Correct: "He is a fast driver". And "Drive quick" is informal; the correct adverb is "quickly" or "fast" (which does not change form).
Trick to remember it
- •"Quick" almost always precedes a noun and describes something brief ("a quick look", "a quick call").
- •"Fast" describes speed itself ("a fast car", "run fast").
- •If you can substitute with "brief": use "quick".
- •If you can substitute with "rapid": use "fast".
Quick rule
- •"Fast" = continuous high speed.
- •"Quick" = short duration or without delay.
Did you know?
"Fast" has a little-known completely opposite meaning: in Old and modern English, "fast" also means "firmly fixed, not moving". "Fast asleep" = deeply asleep (not quickly asleep). "Hold fast" = grip firmly. "Stand fast" = remain firm. This meaning comes from Old English "faest" (firm, fixed). The "fast" meaning speed is a more recent semantic evolution. One word that means both "moving very quickly" and "completely motionless". English at its most paradoxical.
Practise what you learned
Exercise 1 · Pick the right one
She is a very _____ reader. She can finish a novel in a day.
Exercise 2 · Pick the right one
I just need a _____ word with you. It will only take a second.
Exercise 3 · Form the word
Related word pairs
"Fast" is both adjective and adverb; "quickly" is only an adverb and sounds more formal.
"Hard" as an adverb means with effort or intensity; "hardly" means almost not, barely.
Both mean "not easy", but "hard" also means physically firm or working intensely.
"Late" means behind schedule or at an advanced hour; "lately" means recently or in recent times.
Bryan López
Founder of SpeakUP Academy