"Zygote. This cell, formed by the union of an ovum and a sperm (Gr. zygtos, yoked together), represents the beginning of a human being."
[Moore, Keith L. and Persaud, T.V.N. Before We Are Born: Essentials of Embryology and Birth Defects. 4th edition. Philadelphia: W.B. Saunders Company, 1993, p. 1]