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The most common other words for fast are quick, rapid, swift and speedy. For movement you can also say brisk (a brisk walk) or high-speed (a high-speed train); for something done too fast, hasty or hurried; and in casual speech, lightning-fast, super quick or in no time. They overlap, but each has its own habits: a car is fast, a decision is quick, growth is rapid, and justice is swift.
Below: a picker, how the main synonyms differ, fast as an adverb (and why “fastly” is wrong), the other meanings of fast that have nothing to do with speed, and a short practice set.
Quick picker
| Describing… | Instead of fast, try | Example |
|---|---|---|
| a vehicle, a runner, a machine | speedy, high-speed, nippy (British, small cars) | The new trains are high-speed and quiet. |
| an action that takes little time | quick, prompt, speedy | Thanks for the quick reply. |
| growth, change, decline | rapid, swift, sharp, steep | The town saw rapid growth in the 1990s. |
| a response or result, praised | swift, prompt, speedy | We wish you a speedy recovery. |
| walking or a pace | brisk, quick, rapid | We set off at a brisk pace. |
| something done too fast | hasty, hurried, rushed | It was a hasty decision, and we regret it. |
| a sudden movement | sudden, abrupt, lightning-quick | He made a sudden grab for the ball. |
| casual praise for speed | lightning-fast, super quick, blazing fast | The new laptop is lightning-fast. |
| a busy, intense environment | fast-paced, high-pressure, hectic | She works in a fast-paced newsroom. |
How the main synonyms differ
- fast – high speed of movement or operation: a fast car, a fast runner, a fast computer, a fast internet connection. It describes the thing that moves or works.
- quick – taking little time: a quick shower, a quick question, a quick learner. “A fast shower” sounds odd; “a quick shower” is natural. Quick also describes a mind: “She’s very quick” means she understands things fast.
- rapid – happening at high speed or rate, especially change: rapid growth, rapid progress, a rapid heartbeat, rapid fire. It is a little more formal and common in reports and news.
- swift – fast and smooth, often with approval: a swift response, swift justice, a swift kick. It sounds slightly literary or journalistic.
- speedy – quick and welcome: a speedy recovery, speedy delivery. Friendly, a little informal.
- prompt – done without delay, on time: prompt payment, a prompt reply. It is about not waiting, not about speed in motion.
- brisk – quick and energetic: a brisk walk, brisk business (many customers), a brisk manner (efficient, a bit curt).
- hasty, hurried, rushed – too fast to be careful. These are negative: a hasty conclusion, a hurried goodbye, a rushed job.
A useful test: if you can ask “How fast does it go?”, fast fits. If you would ask “How long did it take?”, quick usually fits better.
Fast as an adverb: fast, quickly, rapidly
Fast is both an adjective and an adverb, with the same form: “a fast runner” and “She runs fast”. There is no word “fastly” in standard English.
| Instead of “fast” (adverb) | Example | Note |
|---|---|---|
| quickly | Please reply quickly. | the most general swap |
| rapidly | Prices rose rapidly. | for change and trends |
| swiftly | The police acted swiftly. | formal, approving |
| promptly | The meeting started promptly at nine. | on time, without delay |
| at speed, at full speed | The van was travelling at speed. | movement, often in reports |
| in no time, in a flash, in a heartbeat | The kids finished their dinner in no time. | casual |
| right away, straight away, immediately | I’ll send it right away. | about starting now, not speed |
Position matters: fast as an adverb goes after the verb (“drive fast”, not “fast drive”), while quickly can also go before it (“He quickly closed the door”).
Stronger and more vivid words
- lightning-fast, blazing fast, blistering (a blistering pace) – very fast, informal or sporty.
- breakneck – dangerously fast: “at breakneck speed”.
- headlong – fast and without thinking: “a headlong rush into the market”.
- meteoric – extremely fast rise in a career: “her meteoric rise to fame”.
- whirlwind – fast and exciting: “a whirlwind romance”, “a whirlwind tour”.
- express – designed to be fast: express delivery, an express train.
- nimble, agile – quick and light in movement: nimble fingers, an agile goalkeeper.
For comparisons rather than single words (“as fast as lightning”, “like a bat out of hell”), see similes for speed and idioms for speed; for running in particular, metaphors for running fast.
The other meanings of fast
Fast has several meanings that have nothing to do with speed, and its synonyms change completely:
| Meaning | Example | Synonyms |
|---|---|---|
| firmly fixed, secure | The boat was made fast to the pier. / Hold fast! | secure, tight, firm |
| deeply (asleep) | The baby is fast asleep. | sound asleep, deeply asleep |
| loyal (friends) | They became fast friends. | close, firm, devoted |
| (of colour) not fading | Is this dye fast? / colourfast | permanent, fade-resistant |
| (of a clock) ahead | My watch is five minutes fast. | ahead |
| to go without food (verb) | Many Muslims fast during Ramadan. | abstain from food, go without |
| a period without food (noun) | She broke her fast at sunset. | fasting period |
That last sense is where breakfast comes from: the first meal “breaks” the night’s fast. The idea of fast as “firm, fixed” is the older one in English; the sense of speed developed from it (from “firmly” to “vigorously” to “quickly”).
Opposites of fast
- For speed: slow, unhurried, leisurely (positive), sluggish (negative).
- For time taken: long, lengthy, drawn-out.
- For responses: delayed, late, tardy (formal).
- For the “firm” sense: loose.
Common mistakes
- “He drove very fastly.” Use fast or quickly: “He drove very fast.”
- “Can I ask a fast question?” Use quick for things that take little time: “a quick question”.
- “The company had a speedy growth.” Growth is usually rapid or fast; and drop the article: “The company grew rapidly” or “The company saw rapid growth.”
- “Thank you for your hasty reply.” Hasty means too fast and careless. You mean quick or prompt.
- “The baby is fast sleeping.” The phrase is fixed: “fast asleep”.
- Using “swift” in a casual text. “That was swift!” can sound mock-formal. In casual messages, “That was quick!” is more natural.
Practice
Replace fast with the best word in brackets.
- Could I ask you a fast question before you go? (quick / rapid / swift)
- The country’s population grew fast after the war. (rapidly / hastily / promptly)
- We wish your father a fast recovery. (speedy / hasty / breakneck)
- They made a fast decision and later regretted it. (hasty / prompt / nimble)
- The government’s fast response prevented a crisis. (swift / hurried / brisk)
- We went for a fast walk along the beach before breakfast. (brisk / hasty / meteoric)
- Correct the mistake: “She finished the test fastly.”
Answers: 1. quick 2. rapidly 3. speedy 4. hasty 5. swift 6. brisk 7. “She finished the test quickly” (or “fast”).
Quick answers
What is a fancy word for fast? Swift, rapid or expeditious (very formal: “an expeditious resolution”). For movement, fleet-footed is literary.
What is a word for very fast? Lightning-fast, blistering, breakneck (dangerously fast) or meteoric (a rise).
Is “fastly” a word? No. The adverb of fast is fast: “He runs fast.” Use quickly or rapidly if you want an -ly form.
What is the difference between fast and quick? Fast is about speed of movement or operation (a fast car); quick is about taking little time (a quick lunch). Often both work: a fast/quick learner.
What is another word for fast-paced? Hectic, busy, high-pressure, dynamic (positive) or frantic (negative).
What does “fast” mean in “fast asleep”? Firmly or deeply – the old “fixed” sense of fast, not speed.
How similes and metaphors build on words like these is explained in our guide to figurative language.