A reproductive cell that fuses with another gamete to form a zygote. Examples of gametes are ova and spermatozoa. Gametes are haploid, i.e. they contain half the normal (diploid) number of chromosomes; thus when two fuse, the diploid number is restored (see fertilization). Gametes are formed by meiosis. Gametes often differ in size, the smaller (usually male) gamete being known as the microgamete and the larger (usually female) as the macrogamete. See also sexual reproduction.