還元反応

• Reading: かんげんはんのう
• Romaji: kangen hanno
• Kanji breakdown: 還 (kan) — to return; 元 (gen) — origin, source; 反 (han) — to react; 応 (o) — to respond
• Pronunciation: /kaŋ.ɡeɴ.haɴ.noː/

Meaning

Reduction reaction; a chemical reaction in which a substance gains electrons (or loses oxygen or gains hydrogen). The counterpart of oxidation.

In chemistry, 還元反応 (reduction reaction) always occurs alongside 酸化反応 (oxidation reaction) as a redox pair (酸化還元反応). Reduction is defined as the gain of electrons, loss of oxygen, or gain of hydrogen. The term appears in organic synthesis, electrochemistry (電気化学), metallurgy (冶金), and biochemistry (particularly in metabolic pathways such as 解糖系 and クエン酸回路). The agent that causes reduction is called 還元剤 (reducing agent).

Examples

1. 酸化銅に水素を作用させると還元反応が起こり、純粋な銅と水が生成される。 When hydrogen is applied to copper oxide, a reduction reaction occurs, producing pure copper and water.
2. 電気化学では、陰極において還元反応が進行し、陽極では酸化反応が起きる。 In electrochemistry, a reduction reaction proceeds at the cathode, while an oxidation reaction occurs at the anode.
3. 生体内の代謝では、酸化反応と還元反応が対になって進行し、エネルギーが産生される。 In metabolic processes within living organisms, oxidation and reduction reactions proceed in pairs, generating energy.

Usage Guide

Context: chemistry, electrochemistry, biochemistry, materials science

Tone: technical, academic

Origin & History

Sino-Japanese scientific compound: 還元 (kangen) — reduction, restoring to original state + 反応 (hanno) — reaction. 還元 combines 還 (to return) and 元 (origin, source), expressing the idea of 'returning to an original state' (e.g., restoring an oxide to its pure metal form).

Cultural Context

Era: Meiji-Modern

Generation: Adult

Social background: Educated