- a group of four.
- the number four.
- Cell Biology. a group of four chromatids formed by synapsis at the beginning of meiosis.
- Chemistry. a tetravalent or quadrivalent element, atom, or group.
Origin of tetrad
1645–55; < Greek tetrad- (stem of tetrás) group of four
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for tetrad
The tetrad for the perfect figure—the cube, length, depth, and width.Notes and Queries for Worcestershire
Having sent for that Brhman, he learnt from him a tetrad of gths.The Gtakaml
They are aborting members of the tetrad, and appear to have been used as food by the other spores.Ancient Plants
Marie C. Stopes
Such an axis of symmetry is known as a tetrad axis of symmetry.
If the second cell division plane is formed at right angles to the first, a cell surface or tetrad is formed.Outlines of Dairy Bacteriology, 8th edition
H. L. Russell
- a group or series of four
- the number four
- botany a group of four cells formed by meiosis from one diploid cell
- genetics a four-stranded structure, formed during the pachytene stage of meiosis, consisting of paired homologous chromosomes that have each divided into two chromatids
- chem an element, atom, group, or ion with a valency of four
- ecology a square of 2 × 2 km used in distribution mapping
C17: from Greek tetras, from tettares four
Word Origin and History for tetrad
1650s, from Greek tetras (comb. form tetrad-) "group of four" (see tetra-).
Online Etymology Dictionary, © 2010 Douglas Harper
- 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.
- 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.