substitute

Act as a substitute.

Be a substitute.

“The young teacher had to substitute for the sick colleague”

“The skim milk substitutes for cream--we are on a strict diet”

Put in the place of another; switch seemingly equivalent items.

“substitute regular milk for fat-free milk”

Serving or used in place of another.

Capable of substituting in any of several positions on a team.

Artificial and inferior.

“substitute coffee”

Someone who takes the place of another (as when things get dangerous or difficult).

An athlete who plays only when a starter on the team is replaced.

A person or thing that takes or can take the place of another.