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

substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)

take the place or move into the position of

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.