Enantiomers are a pair of stereoisomers that are non-superimposable mirror images of one another, related like a left and a right hand. They matter because they share almost all physical properties yet can behave very differently in a chiral environment, such as in the body. A pair of enantiomers contrasts with diastereomers, which are stereoisomers that are not mirror images of each other.

对映异构体是一对互为镜像且不能重合的立体异构体,二者的关系如同左手与右手。它们之所以重要,是因为两者几乎共有全部物理性质,却可能在手性环境(如体内)中表现得很不相同。一对对映异构体与非对映异构体形成对照,后者是彼此不为镜像关系的立体异构体。