Amount of substance is the physical quantity that measures the number of identical entities (such as atoms, molecules, or ions) of which a sample is composed. It is one of the base quantities in chemistry and is measured in moles. It must not be confused with mass: two samples of equal mass can contain very different amounts of substance.

物质的量是衡量样品由多少相同基本单元(如原子、分子或离子)构成的物理量。它是化学中的基本量之一,以摩尔为单位。它不应与质量混淆:质量相等的两份样品所含的物质的量可能相差很大。