Толковый словарь английского языка - density

noun (plural -ties) Date: 1598 the quality or state of being dense, the quantity per unit volume, unit area, or unit length: as, the mass of a substance per unit volume, the distribution of a quantity (as mass, electricity, or energy) per unit usually of space (as length, area, or volume), the average number of individuals or units per space unit , 3. the degree of opacity of a translucent medium, the common logarithm of the opacity