How to say "velocity" in Japanese

Choosing the right word

速度そくどJLPT N3approx.Common
nounCovers 'velocity' in its general scientific or technical sense: the rate of motion of an object, often with direction implied. Use this for physics and engineering contexts.
その男おとこは一定いっていの速度そくどで車くるまを運転うんてんした。↗
The man drove his car at a uniform speed.
球速きゅうそくCommon
nounA narrow word meaning specifically the speed of a pitched baseball, which is one sense of 'velocity' in sports English. Outside baseball it is not the word you want.
速さはやさCommon
nounEssentially 'speed' or 'quickness', the everyday way to say how fast something moves or happens. For the technical sense of 'velocity', 速度 is usually the better choice.
エイズウイルスの拡散かくさんは恐おそるべき速はやさで進すすんでいる。↗
The speed of the spread of AIDS is horrifyingly fast.

For most senses of 'velocity' use 速度 (or 「速さ」 for everyday speed), but when 'velocity' means the speed of a pitched ball, use 球速.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

Japanese equivalents

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