Translation guide
The English word "fast" covers speed, firmness, and abstinence. This guide helps learners choose the right Japanese expression for each meaning.
Describing something that moves or happens at high speed.
The most common adjective for speed. Use for vehicles, animals, actions, etc.
This car is very fast.
He runs fast.
Means 'early' or 'quick' in terms of time. Often used for prompt actions or early completion.
Do not use 早い for physical speed; use 速い instead.
Means 'nimble' or 'swift', often implying agility.
The cat's movements are fast.
A noun or na-adjective meaning 'rapid', often used in formal or technical contexts.
rapid development
Describing something that is tightly fixed, stuck, or not easily moved.
Means 'firm', 'solid', or 'tight'. Used for objects, knots, handshakes, etc.
This screw is fast (tight).
Please tie it fast (tightly).
Means 'hard' or 'firm'. Can describe a tight grip or a solid object.
Means 'immovable' or 'not budging', used for something firmly fixed.
The rock was fast (didn't budge).
Abstaining from food, often for religious or health reasons.
Describing colors or dyes that do not run or fade.
Sleeping deeply.
A close, loyal friend.
Both are read はやい. 速い is for physical speed (fast car, fast runner). 早い is for time-related quickness (early morning, prompt reply). Using the wrong kanji can confuse the meaning.
English 'fast' in 'fast asleep' does not mean speed. Do not use 速い or 早い. Use ぐっすり or 熟睡.
He gives a firm handshake.