A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke"), or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo. In single-celled organisms, the zygote divides to produce offspring, usually through meiosis.
A zygote is always synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development. Zygotes are usually produced by a fertilization event between two haploid cells—an ovum (female gamete) and a sperm cell (male gamete)—which combine to form the single diploid cell. Such zygotes contain DNA derived from both parents, and this provides all the genetic information necessary to form a new individual.