Pronunciation: (te'trad), [key]
1. a group of four.
2. the number four.
3. Cell Biol.a group of four chromatids formed by synapsis at the beginning of meiosis.
4. Chem.a tetravalent or quadrivalent element, atom, or group.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.