atomic mass
noun [ C or U ] chemistry specialized uk/əˌtɒm.ɪk ˈmæs/ us/əˌtɑː.mɪk ˈmæs/
原子质量（某化学元素同位素的质量，通常以原子质量单位的形式表达）
the mass of a specific isotope of a particular chemical element, usually expressed in atomic mass units
Compare: relative atomic massatomic weight