放射線

• Reading: ほうしゃせん
• Romaji: houshasen
• Kanji breakdown: 放 (hou) — release, emit, set free; 射 (sha) — shoot, radiate; 線 (sen) — line, ray
• Pronunciation: /hoː.ɕa.seɴ/

Meaning

Radiation. Energy emitted in the form of waves or particles, especially from radioactive substances.

A noun used in science, medicine, and environmental contexts for ionising radiation. Distinct from 放射能 (houshanou, radioactivity — the property of emitting radiation) and 放射性物質 (houshasei busshitsu, radioactive material). Common collocations include 放射線治療 (houshasen chiryou, radiation therapy), 放射線量 (houshasen ryou, radiation dose), and 放射線技師 (houshasen gishi, radiological technologist). Became widely known in everyday Japanese after the Fukushima nuclear disaster in 2011.

Examples

1. 放射線を利用してがんの治療を行う方法がある。 There are methods of treating cancer using radiation.
2. 原発事故の後、放射線の測定が毎日行われた。 After the nuclear plant accident, radiation levels were measured every day.
3. 放射線から体を守るために鉛の壁が使われている。 Lead walls are used to protect the body from radiation.

Usage Guide

Context: science, medicine, nuclear energy

Tone: serious

Origin & History

From Sino-Japanese: 放 (hou, release/emit) + 射 (sha, shoot/radiate) + 線 (sen, line/ray). Literally 'emitted rays' — energy that is shot outward in lines from a source.

Cultural Context

Era: Modern

Generation: All ages

Social background: Universal