This fine word is often used by molecular biologists and protein chemists to describe proteins that are comprised of separate subunits. However, this word has a long and distinguished history outside of biology, as I recalled when I found it in a crossword puzzle in a book published by Dell;
Moiety (MOY-uh-tee) [Old French meitiet, from Late Latin medietas, from Latin medius, "middle."]
- One of two equal parts; a half.
- An indefinite part; a small portion or share.
- One of two basic tribal subdivisions.
Usage: Tom divided the cake and Becky ate with good appetite, while Tom nibbled at his moiety.