紫外線

• Reading: しがいせん
• Romaji: shigaisen
• Kanji breakdown: 紫 (shi) — purple, violet; 外 (gai) — outside, beyond; 線 (sen) — line, ray
• Pronunciation: /ɕi.ɡa.i.seɴ/

Meaning

Ultraviolet rays; UV radiation. Commonly discussed in relation to sun protection and skincare.

A scientific term widely used in everyday Japanese, particularly in weather forecasts, skincare, and health discussions. Common collocations include 紫外線対策 (UV protection measures) and 紫外線が強い (UV rays are strong). Frequently heard in summer and in beauty product marketing.

Examples

1. 夏は紫外線が強いので日焼け止めを塗ったほうがいい。 You should put on sunscreen in summer because the UV rays are strong.
2. 紫外線対策として帽子とサングラスを持っていく。 I'm bringing a hat and sunglasses as UV protection measures.
3. 長時間紫外線を浴びると肌に悪影響がある。 Prolonged exposure to UV rays can have harmful effects on your skin.

Usage Guide

Context: weather, skincare, health

Tone: neutral

Origin & History

Compound of 紫外 (shigai, beyond violet) + 線 (sen, ray). A calque of the Western scientific term 'ultraviolet,' referring to light beyond the violet end of the visible spectrum.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal