a person or thing equal to another in value or measure or force or effect or significance etc

serving or used in place of another

put in the place of another; switch seemingly equivalent items

be a substitute

an artificial or inferior substitute or imitation

a thing or person that immediately replaces something or someone

(medicine) something that can be used as a substitute (especially any medicine that may be taken in place of another)

a person or thing considered inferior to another or others.