alternates
al-ter-nates
noun
Persons or things designated to serve as a substitute or reserve.
"We have several alternates ready for the team."
verb
To occur or cause to occur in repeated succession.
"The traffic light alternates between red and green."
Thesaurus
Synonyms: alternate, alternative, substitute, secondary, take turns, understudy, jump, surrogate, replacement, flip, interchange, flip-flop