Density (d) depends upon the mass (m) and volume (v) of a substance. The mass depends upon the amount of matter in a substance, whereas volume is the amount of space that a substance takes up. Mathematically, density is equal to a ratio where d = m/v. Although mass and volume are extensive properties (depend upon how much matter is present), density is considered to be an intensive property (does not depend upon how much matter is present). Although the aforementioned definition of density in terms of volume is a popular one, one needs to be aware that this definition needs to be slightly modified when dealing with different dimensional spaces. In physics, one may also be dealing with various types of density which include linear density (mass/length) as well as surface density (mass/area). Regardless of the type of density, it remains an intensive property. Other types of intensive properties include boiling point, melting point, conductivity, malleability, hardness, luster, etc.