Langman’s Medical Embryology On the Beginning of Life

T.W. Sadler, Langman’s Medical Embryology, 10th edition. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. p. 11.

“Development begins with fertilization, the process by which the male gamete, the sperm, and the femal gamete, the oocyte, unite to give rise to a zygote.”