specific gravity

specific-gravity的词性：
n.Abbr. sg, sp gr（名词）缩写 sg， sp gr

1. The ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water at 4⁼C (39⁼F) or of a gas to an equal volume of air or hydrogen under prescribed conditions of temperature and pressure.
比重：一固体或液体的质量与温度为4⁼C(39⁼F)同体积的蒸溜水的质量之比，或者是一气体质量与处于规定的温度及压力条件下同体积的空气或氢气的质量之比