平衡

• Reading: へいこう
• Romaji: heiko
• Kanji breakdown: 平 (hei) — flat, level, equal; 衡 (kō) — balance, weigh, horizontal bar
• Pronunciation: /heː.koː/

Meaning

Equilibrium; balance. A state in which opposing forces or influences are equal and stable, used across chemistry, physics, biology, and economics.

Central to thermodynamics and chemistry, 平衡 describes a state where forward and reverse processes occur at equal rates (dynamic equilibrium) or all forces are balanced (static equilibrium). In chemistry, 化学平衡 refers to the state where reactant and product concentrations remain constant. Also used in ecology and social science to describe stable, self-sustaining systems.

Examples

1. 化学反応が平衡に達すると、反応物と生成物の濃度が一定になる。 When a chemical reaction reaches equilibrium, the concentrations of reactants and products remain constant.
2. 生態系の平衡は一種の生物が絶滅することで崩れることがある。 The equilibrium of an ecosystem can be disrupted by the extinction of a single species.
3. 体内の水分と電解質の平衡を保つことが健康維持に不可欠だ。 Maintaining the balance of fluids and electrolytes in the body is essential for good health.

Usage Guide

Context: chemistry, physics, biology, ecology

Tone: analytical

Origin & History

From Classical Chinese. 平 means flat or level, and 衡 originally referred to the crossbar of a balance scale. Together they evoke the image of a perfectly balanced scale — the defining metaphor of equilibrium.

Cultural Context

Era: Classical–Modern

Generation: Adults (academic)

Social background: Academic/Scientific