rapid

The word “rapid” means happening or moving very quickly. In plain terms, fast; happening in a short amount of time.

“Rapid” is pronounced RA-pihd (/ˈɹæpɪd/ in IPA).

Here is “rapid” used in a sentence: “The company saw rapid growth over the last two years.”

“Rapid” is an adjective.

The word “rapid” comes from Latin. From Latin rapidus, "hurried, seizing," from rapere, "to snatch or seize" — the same root that gives us rapture and rapacious.

“Rapid” is a fairly common word in modern English, usually learned at around the B1 level.

All three describe speed, but they attach to different things. Fast usually describes moving objects or people (a fast car), quick often stresses short duration (a quick reply), and rapid typically describes the pace of processes or changes, as in rapid growth or rapid decline. Rapid also sounds more formal and is common in technical and journalistic writing.

Rapid is an adjective, so it modifies nouns: a rapid response, rapid change. Rapidly is the adverb, so it modifies verbs: the disease spread rapidly. Saying "it spread rapid" is a common mistake; use rapidly whenever you are describing how an action happens.

Rapid pairs most naturally with nouns describing change or motion over time: rapid growth, rapid change, rapid decline, rapid expansion, rapid progress, and rapid heartbeat. Phrases like rapid response and at a rapid pace are also very frequent. These collocations reflect the core meaning of rapid: happening or moving very quickly.