官能团是决定有机化合物的化学性质的原子或原子团,Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.基团则不一定决定化学性质.但实际运用中,似乎functional group,group,moiety常常是指一个意思. 烷基是比较特殊的基团,因为烷基不能决定有机物的化学性质,所以不是官能团,但其它烃基,如：烯烃基,炔烃基,苯基等则属于官能团.
