tetrad

A group or set of four.

A tetravalent atom, radical, or element.

A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.

A group of four haploid cells, such as spores, formed by meiotic division of one mother cell.

The number four; also, a collection of four things. Also quadrad.