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.
物質單位體積的質量叫做密度。 - Within the remainder of the dielectric the net charge per unit volume remains zero.
在電介質的其餘部分，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.
物質單位體積的質量叫做密度。 - Within the remainder of the dielectric the net charge per unit volume remains zero.
在電介質的其餘部分，單位體積的靜電荷仍為零。
