a person or thing taking the place of, acting for, another
alternative
Cases of word usage
1) as an alternative of substitute (instead)
2) to put (something) back in its place; to take the place of (a person, thing); to supply, use, (a person, thing) as a substitute (replace)
3) acting as a substitute (surrogate)
4) experienced by watching or reading about other people doing it; experienced as a substitute for another person (vicarious)