Any of two or more nuclei with the same mass number and atomic number that have different radioactive properties and can exist in any of several energy states for a measurable period of time.

• 同质异能素两种或更多种具有相同的质子数和原子数，但有不同的辐射特性并能在几种能量状态中的任一种里存在一段可测量时间的原子核中