replacement
re-place-ment
noun
The act of putting something new or different in place of something old.
"The faulty part needs a quick replacement."
noun
A person or thing that takes the place of another.
"We need to find a suitable replacement for Sarah."
Thesaurus
Synonyms: replacing, successor, substitute, surrogate, alternate, replenishment, renewal, refilling, permutation, transposition, substitution, switch