質量

• Reading: しつりょう
• Romaji: shitsuryo
• Kanji breakdown: 質 (shitsu) — substance, matter | 量 (ryo) — quantity, amount
• Pronunciation: /ɕi.tsɯ.ɾjo.ɯ/

Meaning

Mass; the amount of matter in an object (physics). Distinguished from weight, which varies with gravitational force.

A fundamental concept in physics. 質量 remains constant regardless of gravity, whereas 重さ (weight) changes. Key collocations include 質量保存の法則 (law of conservation of mass), 相対論的質量 (relativistic mass), and 質量数 (mass number). Famous in Einstein's equation E=mc², relating mass and energy.

Examples

1. アインシュタインの公式E=mc²は、質量とエネルギーの等価性を示している。 Einstein's formula E=mc² demonstrates the equivalence of mass and energy.
2. この粒子の質量は非常に小さく、標準的な計測装置では測定が難しい。 The mass of this particle is extremely small, making it difficult to measure with standard instruments.
3. 月面では重力加速度が地球の六分の一であるため、体重は変化するが質量は変わらない。 On the Moon, where gravitational acceleration is one-sixth that of Earth, weight changes but mass does not.

Usage Guide

Context: physics, chemistry, science education

Tone: technical

Origin & History

Compound of 質 (shitsu) meaning 'substance, matter' and 量 (ryo) meaning 'quantity, amount'. Coined in the Meiji period to translate the physics concept of 'mass' introduced from Western science.

Cultural Context

Era: Meiji–Modern

Generation: Students and scientists

Social background: Academic