Translation guide
The concept of momentum in English covers physical motion, figurative progress, and social dynamics. In Japanese, there is no single direct equivalent; instead, different words and phrases are used depending on whether you mean physical momentum, gaining speed, losing steam, or the force of a trend.
The quantity of motion of a moving body, measured as mass times velocity.
The standard physics term for momentum. Used in scientific and technical contexts.
the law of conservation of momentum
Refers to force, energy, or impetus. Can be used for physical momentum in everyday language, but is broader.
The ball had too much momentum.
The force or speed of movement that keeps something going, such as a project, career, or event.
The most common word for figurative momentum. Implies energy, force, or impetus that drives something forward.
That team is riding a wave of momentum.
Often used for momentum gained from a small start, like a snowball effect. Common in phrases like 弾みがつく (gain momentum).
Loanword from English, used in business or sports contexts, but less natural than 勢い.
Maintain the momentum of the project.
The process of increasing speed, force, or progress.
Literally 'momentum attaches'. Means to gain momentum or pick up speed.
The economic recovery is gaining momentum.
Similar to 勢いがつく, but often implies a trigger or initial push.
His goal gave the team momentum.
Means 'to accelerate'. Can be used figuratively for momentum.
The reform movement is gaining momentum.
The loss of speed, force, or progress.
A popular movement or widespread trend that is gaining force.
Both mean momentum, but 勢い is broader and more common. 弾み often implies a bounce or trigger that starts momentum, like a spring or a lucky break. Use 勢い for general momentum, and 弾み when emphasizing the initial push or snowball effect.
His remark got the conversation going (gave it momentum).
In many cases, English 'momentum' is better expressed with a verb like 加速する (accelerate) or 勢いづく (gain momentum). Using モメンタム can sound unnatural outside of business jargon.
The momentum of reform is unstoppable.
Once you succeed, you gain momentum.
歴史の潮流に逆らえない。
You can't go against the momentum of history.