反応する

• Reading: はんのうする
• Romaji: hannou suru
• Kanji breakdown: 反 (han) — to return, oppose; 応 (ou) — to respond, answer
• Pronunciation: /ha.ɴ.noː.sɯ.ɾɯ/

Meaning

To react; to respond. Used for physical, chemical, emotional, and social reactions.

A する verb formed from the noun 反応 (reaction/response). Versatile across domains: chemical reactions in science, audience reactions, allergic reactions in medicine, and emotional responses. Common phrases include アレルギー反応 (allergic reaction) and 反応が早い (quick to respond).

Examples

1. 薬を飲んだ後、体がすぐに反応した。 After taking the medicine, my body reacted right away.
2. その提案に対して誰も反応しなかった。 Nobody reacted to that proposal.
3. 彼女の投稿に多くの人が反応している。 Many people are reacting to her post.

Usage Guide

Context: science, medicine, social media

Tone: neutral

Origin & History

Compound of 反 (han, to return/oppose) and 応 (ou, to respond). Together they mean to send back a response — reacting to a stimulus.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal