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

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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

In psychology, the "dark tetrad" refers to a group of four personality traits.

From Salon ● Apr. 16, 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

The mother cell undergoes meiosis to form a tetrad of cells, which separate to form the pollen grains.

From Textbooks ● Jan. 1, 2015

They are parallel to the edges of the cube, and in the different classes coincide either with tetrad or dyad axes of symmetry.

From Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 "Crocoite" to "Cuba" by Various

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