A nuclear isomer refers to a metastable state of an atomic nucleus in an excited state.
異性核の崩壊過程は、通常の放射性崩壊とは異なる場合がある。
The decay process of a nuclear isomer can differ from ordinary radioactive decay.
Compound of 異性 (isomerism, from 異 'different' + 性 'property') and 核 (nucleus). The exact historical derivation is uncertain; the term is a modern technical coinage.