Action, effect, or functioning — the operation or influence produced (often used in chemistry, medicine, or physics).
この薬には強い鎮痛作用がある。
This medicine has a strong analgesic (pain-relieving) effect.
重力の作用で物体は下に落ちる。
Objects fall downward due to the action of gravity.
その政策は経済にどのような作用を及ぼすだろうか。
What kind of effect will that policy have on the economy?