tetrad

[ te-trad ]

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.

tetrad

/ ˈtɛtræd /

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

/ tĕt′răd′ /

1. 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.
2. See more at meiosis
3. 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.
4. See more at spermatogenesis

Word History and Origins

Origin of tetrad¹

1645–55; < Greek tetrad- (stem of tetrás ) group of four

Word History and Origins

Origin of tetrad¹

C17: from Greek tetras, from tettares four

Example Sentences

Studying cryptocurrency through the psychological lens of the dark tetrad offers insight into why people want to buy crypto.

From Salon

The Current Newspapers, the tetrad of hyperlocal printed newspapers in Northwest D.C., is in bankruptcy.

From Washington Post

It was the end of an eclipse series known as a lunar eclipse tetrad.

From Scientific American

“Some prophecy teachers are declaring boldly that this tetrad just ahead signals that something is getting ready to happen, which will change the world forever,” Baxter said on his website.

From The Guardian

This weekend's blood moon will be the last in a series of four lunar eclipses, dubbed a tetrad, over the last two years.

From National Geographic