per unit volume的用法和樣例：
例句
- The mass of one unit of volume of a material is called its density.
物質(zhì)單位體積的質(zhì)量叫做密度。 - Within the remainder of the dielectric the net charge per unit volume remains zero.
在電介質(zhì)的其余部分，單位體積的靜電荷仍為零。 - The mass of one unit of volume of a material is called its density.
物質(zhì)單位體積的質(zhì)量叫做密度。 - Within the remainder of the dielectric the net charge per unit volume remains zero.
在電介質(zhì)的其余部分，單位體積的靜電荷仍為零。
