replacement

noun

1. the act of replacing.
2. a person or thing that replaces another: summer replacements for vacationing staff; a replacement for a broken dish.
3. Military. a sailor, soldier, or airman assigned to fill a vacancy in a military unit.
4. Also called metasomatism. Geology. the process of practically simultaneous removal and deposition by which a new mineral grows in the body of an old one.

noun

1. the act or process of replacing
2. a person or thing that replaces another
3. geology the growth of a mineral within another of different chemical composition by gradual simultaneous deposition and removal
4. a process of fossilization by gradual substitution of mineral matter for the original organic matterAlso called: petrification