natural radiation; background radiation
Refers to ionizing radiation from natural sources such as cosmic rays, terrestrial radionuclides, and internal body radioactivity. Often used in scientific, environmental, and health contexts.
Natural radiation constantly falls on our bodies from space and the earth.
The natural radiation level in this area is slightly higher than the national average.
General term for radiation, including both natural and artificial sources. 自然放射線 specifically refers to radiation from natural sources.
Artificial or man-made radiation, as opposed to natural radiation.
Loanword equivalent often used in technical contexts, synonymous with 自然放射線.
Compound of 自然 (しぜん, 'nature') + 放射線 (ほうしゃせん, 'radiation'). The term is a straightforward modern technical coinage.