How to say "emission" in Japanese
Choosing the right word
- 放射ほうしゃnoun, suru verb, transitive verbCovers emission in the sense of radiation, such as energy or rays radiating outward. It is the natural choice when the English refers to radioactive or electromagnetic emission rather than releasing a substance.
- 放出ほうしゅつnoun, suru verb, transitive verb, intransitive verbUsed for the emission or release of something outward — energy, particles, gases, or radiation. It suits contexts where something held inside is discharged or sent out into space or the surroundings.
- 発散はっさんnoun, suru verb, transitive verb, intransitive verbMatches emission as emanation or diffusion, something spreading out from a source. It also has everyday uses (diverging, venting feelings), so it is seldom the word you want for physical emission like exhaust; think 'spreading outward' instead.
- 発光はっこうnoun, suru verb, intransitive verbRestricted to emission of light — luminescence or radiation of light. Use it when the English says 'emission of light' or in scientific talk of light-emitting phenomena; it does not cover gases, heat, or particles.
- 排出はいしゅつnoun, suru verb, transitive verbThe everyday word for emission of waste or exhaust, especially CO2 and other pollutants — 'carbon emissions' is the classic context. It implies discharging something unwanted out of a system, body, or machine.
Choose 排出 for waste/gas emissions like CO2, 放出 for release of energy or particles, 発光 specifically for light emission, 放射 for radiation, and 発散 for diffusion or emanation.
Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only
Japanese equivalents
See also
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