Definition: Monaphase is a process in biology where an organism divides its cells into two equal halves. It occurs during the cell division of a sperm and egg, or during fertilization of an egg by a sperm. In monaphase, each cell divides evenly between two nuclei, with one nucleus remaining undivided and released as waste. This is different from prophase where each cell has been divided into four equal halves, and metaphase, where each cell has been divided into two equal halves.