Tetrad

noun
1.
a group of four.
2.
the number four.
3.
Cell Biology. a group of four chromatids formed by synapsis at the beginning of meiosis.
4.
Chemistry. a tetravalent or quadrivalent element, atom, or group.
noun
1.
a group or series of four
2.
the number four
3.
(botany) a group of four cells formed by meiosis from one diploid cell
4.
(genetics) a four-stranded structure, formed during the pachytene stage of meiosis, consisting of paired homologous chromosomes that have each divided into two chromatids
5.
(chem) an element, atom, group, or ion with a valency of four
6.
(ecology) a square of 2 × 2 km used in distribution mapping

tetrad tet·rad (tět’rād’)
n.

A group or set of four.

A tetravalent atom, radical, or element.

A group of four chromatids formed from each of a pair of homologous chromosomes that split longitudinally during the prophase of meiosis.

tetrad
(tět’rād’)

A four-part structure that forms during prophase I of meiosis and consists of two homologous chromosomes, each composed of two identical chromatids. During prophase I of meiosis, one chromosome exchanges corresponding segments of genetic material with the other chromosome in the tetrad in the process called crossing over. See more at meiosis.

A group of four cells, as of spores or pollen grains, formed from a parent cell by meiosis. As part of the process of spermatogenesis, a spermatocyte divides into a tetrad of four spermatids, cells which go on to develop into sperm. See more at spermatogenesis.