atomic mass unit
noun [ C ] chemistry specialized uk/əˌtɒm.ɪk ˈmæs ˌjuː.nɪt/ us/əˌtɑː.mɪk ˈmæs ˌjuː.nɪt/ (abbreviation u)
原子质量单位（等于碳－12原子质量的十二分之一）
a unit used for measuring atomic mass, equal to one twelfth of the mass of an atom of carbon in its commonest form, carbon-12