反応

• Reading: はんのう
• Romaji: hannou
• Kanji breakdown: 反 (han) — anti, opposite, return; 応 (nou) — respond, reply, apply
• Pronunciation: /haɴ.noː/

Meaning

Reaction; response. A physical, chemical, or emotional response to a stimulus.

A noun and suru-verb with broad usage across science and daily life. In chemistry, it means a chemical reaction (化学反応, kagaku hannou). In everyday use, it describes how someone responds to news, stimuli, or events. Common patterns include 反応する (hannou suru, to react), 反応を見る (hannou wo miru, see the reaction), and 反応が薄い (hannou ga usui, lukewarm response). Also used for physical reflexes and allergic reactions.

Examples

1. 新商品に対する消費者の反応は上々だった。 Consumer response to the new product was very favorable.
2. 酸とアルカリを混ぜると化学反応が起きる。 Mixing an acid and an alkali causes a chemical reaction.
3. 彼女に話しかけたが全く反応がなかった。 I tried talking to her but got no response at all.

Usage Guide

Context: daily life, chemistry, social media

Tone: neutral

Origin & History

From Sino-Japanese: 反 (han, anti/opposite/return) + 応 (ou/nou, respond/reply). Literally 'responding in return' — an action that occurs in response to a stimulus or force.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal