Definition of tetrad in US English:



  • A group or set of four.

    • ‘Sterile plants produce microspores aborted in tetrads, no visible pollen shed, and parthenocarpic pods bearing no seeds.’
    • ‘In both strains, haploid phenotypes from tetrads yielding four viable spores may be used to measure the strength of crossover interference.’
    • ‘Early microsporogenesis events are important to establish the shape of the tetrad, the polarity within the tetrad and consequently to determine the aperture pattern of the pollen grain.’
    • ‘Early in meiosis, each pair of homologs comes together to form a tetrad containing two pairs of sister chromatids.’
    • ‘Two-thirds of the tetrads gave rise to four normally growing spores and one spore that formed a microcolony of 10 cells.’


Mid 17th century: from Greek tetras, tetrad- ‘four, a group of four’.