Tetrad (music)
WordNet

noun


(1)   The cardinal number that is the sum of three and one
WiktionaryText

Noun



  1. A group of four things.
  2. A tetravalent atom or radical.
  3. Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.
 
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