Polysemy:  This is the concept that words often have multiple meanings.  Some of these meanings may be similar, but others may be radically different.  Arace horse is different than a clothes horse.  A person may look cool, but that is not the same as his forehead feeling cool.  In the sweltering heat a boy may be cool in his air conditioned car, but going to the senior prom he may look cool driving his car wearing his tuxedo.