# tetrad

> English word · Noun · IPA /ˈtɛtɹæd/ · frequency rank #88,923

## Definitions
1. A group of four things.
2. Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.
3. A group of four haploid and immature pollen grains in tetrahedral fashion produced by meiotic microsporogenesis.
4. A unit of land area of two by two (that is, four) square kilometres.
5. A tetravalent atom or radical.
6. A group of four basis vectors for a four-dimensional manifold in differential geometry.
7. A chord comprised of four notes; a tetrachord.

## Etymology
From Ancient Greek τετράς (tetrás), analysable as tetra- + -ad.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/tetrad