alternate

Synonyms: alternating every second intermittent periodic recurrent recurring rotating

Synonyms: alternative another backup different interchanging makeshift second surrogate temporary

Antonyms: necessary

Synonyms: backup double equivalent fill-in proxy replacement stand-in sub surrogate

Antonyms: necessity

Synonyms: act reciprocally alter blow hot and cold change come and go exchange fill in for fluctuate follow follow in turn interchange intersperse oscillate relieve rotate seesaw shift shilly-shally substitute sway vacillate vary waver yo-yo

Antonyms: continue