molecular weight
Technical term in chemistry; refers to the mass of a molecule relative to the unified atomic mass unit.
The molecular weight of water is about 18.
Please calculate the molecular weight of this compound.
分子 is a molecule, while 分子量 is the numerical weight of that molecule.
Compound of 分子 (molecule) and 量 (quantity, amount). The term is a direct translation of the Western scientific concept of molecular weight.