反作用(はんさよう)

はんさよう
noun
reaction; counteraction; recoil (physics)
science
1. reaction; counteraction; recoil (physics)
In physics, the equal and opposite force described by Newton's Third Law. Describes phenomena such as the recoil of a gun or the thrust that propels a rocket.
作用(さよう)と反作用(はんさよう)の法則(ほうそく)。
The law of action and reaction.
ロケットは反作用(はんさよう)の原理(げんり)で飛(と)ぶ。
Rockets fly on the principle of reaction.
銃(じゅう)を撃(う)つと反作用(はんさよう)で体(からだ)が押(お)し戻(もど)される。
When you fire a gun, the recoil pushes your body back.
2. backlash; adverse reaction; unintended consequence
Figurative use.
急(きゅう)な改革(かいかく)の反作用(はんさよう)が出(で)た。
There was a backlash from the rapid reforms.
薬(くすり)の反作用(はんさよう)に注意(ちゅうい)する。
To watch out for adverse reactions to medication.
規制(きせい)を強(つよ)めた反作用(はんさよう)で、かえって違反(いはん)が増(ふ)えた。
As an unintended consequence of tightening regulations, violations actually increased.

In physics, refers to Newton's Third Law: for every action, there is an equal and opposite reaction. In general use, it describes negative consequences or pushback that result from an action.

Common collocations

Similar words

Related Words

Related: 作用(さよう) (action; effect; function)
Compare: 副作用(ふくさよう) (side effect)
Compare: 反動(はんどう) (recoil, backlash)
Compare: 反発(はんぱつ) (repulsion, opposition)
general
Added 2026.4.6 23:31 · Revised 2026.9.2 13:02
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