tetrad

American  

[te-trad] / ˈtɛ træd /

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.

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tetrad British  

/ 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

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tetrad Scientific  

/ 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

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Etymology

Origin of tetrad

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

Explanation

A tetrad is a group of four things. If you've ordered four pizzas for dinner, you can announce that you are serving a tetrad of pizzas. You can use the noun tetrad to talk about a set of four numbers in math, or a group of four things in various branches of science — one kind of tetrad is a group of four spores in one specific type of yeast. It's more common in non-scientific speech to say quartet or quadruplet. Tetrad comes from a Greek root, the word tetras, "group of four," from tetra, or "four."

Example Sentences

See Examples For:

tetrad

"Sociopathy is very consistent with the dark tetrad of narcissism, psychopathy, Machiavellianism and sadism," explained Dr. Ramani Durvasula, a licensed clinical psychologist and professor of psychology, in an email to Salon.

From Salon ● Feb. 7, 2023

The orientation of each tetrad is independent of the orientation of the other 22 tetrads.

From Textbooks ● Jun. 9, 2022

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

From Scientific American ● Sep. 28, 2015

The tetrad of 1949-50 occurred just after the founding of Israel.

From The Guardian ● Sep. 27, 2015

An element having a valence of one is a monad; of two, a dyad; three, a triad; four, tetrad; five, pentad; six, hexad, etc.

From An Introduction to Chemical Science by Williams, Rufus Phillips