replacement

the act of furnishing an equivalent person or thing in the place of another; "replacing the star will not be easy"

someone who takes the place of another person

an event in which one thing is substituted for another; "the replacement of lost blood by a transfusion of donor blood"

a person or thing that takes or can take the place of another

filling again by supplying what has been used up

a person who follows next in order; "he was President Lincoln's successor"