SynonymDefinitionAntonym.com - English Synonym Dictionary

Someone who takes the place of another person

Do something in turns

Go back and forth; swing back and forth between two states or conditions

Reverse (a direction, attitude, or course of action)

Be an understudy or alternate for a role

Exchange people temporarily to fulfill certain jobs and functions

Of leaves and branches etc; first on one side and then on the other in two ranks along an axis; not paired

Serving or used in place of another

Occurring by turns; first one and then the other

Every second one of a series