1640s, "to exert, as a thing acted upon, an opposite action upon the agent," from re- + act (v.). Chemical sense is from 1944. Related: Reacted; reacting (1610s). For sense development, see reaction. Meaning "perform again" (often re-act) is from 1650s.
例文
1. There 'dbe no telling how John would react to such news as this.
このようなニュースを聞いてジョンがどのように反応するかはまだ分からない。
2.I don 't react anymore when opponents try to niggle me.
相手がけんかをして私を怒らせたとき、私は彼らを相手にしません。
3.Someone allergic to milk is likely to react to cheese.
牛乳アレルギーの人はチーズに対しても副作用がある可能性があります。
4.Peonies react badly to being moved and are best left undisturbed.