Definition of "tetrad" in English

noun

1. A group of four things.

2. (biology) Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.

3. (biology) A group of four haploid and immature pollen grains in tetrahedral fashion produced by meiotic microsporogenesis.

4. (cartography) A unit of land area of two by two (that is, four) square kilometres.

5. (chemistry) A tetravalent atom or radical.

6. (mathematics) A group of four basis vectors for a four-dimensional manifold in differential geometry.

7. (music) A chord comprised of four notes; a tetrachord.