1. A broad ridged tooth in the adult dentition of mammals (see permanent teeth), found at the back of the jaws behind the premolars. There are two or more molars on each side of both jaws; their surfaces are raised into ridges or cusps for grinding food during chewing. In humans the third (and most posterior) molar does not appear until young adulthood: these molars are known as wisdom teeth.
2. Denoting that an extensive physical property is being expressed per amount of substance, usually per mole. For example, the molar heat capacity of a compound is the heat capacity of that compound per unit amount of substance, i.e. it is usually expressed in J K−1 mol−1.