Translation guide
The English adverb 'rapidly' describes an action happening at high speed or in a short time. In Japanese, this is most naturally expressed with adverbs like 速く (hayaku) or 急速に (kyūsoku ni), but the best choice depends on whether you're describing physical speed, quick change, or a fast pace of activity. Sometimes, the idea of 'rapidly' is built into the verb itself.
Describing movement or action that is fast in speed.
The most common and versatile adverb for 'fast' or 'quickly' in physical actions. Used with verbs of motion or action.
彼は速く走った。
He ran rapidly.
Please walk more rapidly.
Implies quick, agile, or nimble movement. Often used for reflexes or deft actions.
The cat moved rapidly.
Means 'in a hurry' or 'hurriedly'. Focuses on the urgency rather than just speed.
He left the house rapidly.
Describing a situation, number, or state that changes quickly over time.
Formal adverb for rapid change, often used in news or business contexts. Implies a steep or sudden shift.
The population is increasing rapidly.
The situation deteriorated rapidly.
Means 'suddenly' or 'abruptly'. Often used for unexpected rapid changes.
Onomatopoeic adverb suggesting steady, vigorous progress or increase. Casual and emphatic.
Describing work, speech, or processes done at a fast rate.
Literally 'at a fast pace'. A natural way to say something is done rapidly.
He finished the work rapidly.
Onomatopoeic adverb for doing things briskly and efficiently, without wasting time.
She gave instructions rapidly and efficiently.
Specifically for speaking rapidly. 'In a fast-mouthed manner'.
He explained rapidly (in fast speech).
速く (hayaku) is for physical speed. 急速に (kyūsoku ni) is for abstract or quantitative rapid change (formal). 急に (kyū ni) is for sudden, often unexpected changes (can be negative).
The car is going rapidly.
Demand is growing rapidly.
It suddenly started raining rapidly.
急速に is formal and often used in written Japanese or news reports. In everyday conversation, 速く or どんどん are more natural for most 'rapidly' situations.
The sky rapidly grew dark.
新しい店がどんどんできている。
New shops are opening rapidly one after another.