Definition of Hydrozoa in English:


plural noun

  • A class of coelenterates which includes hydras and Portuguese men-of-war. Many of them are colonial and some kinds have both polypoid and medusoid phases.

    • ‘The groups Hydrozoa, Scyphozoa and Cubozoa all are generally characterized as having polyps and medusae (although minor lineages have lost medusae and in some cases polyps).’
    • ‘Another feature that is quite common in Hydrozoa but not typical of Scyphozoa is colonial organization.’
    • ‘However, Hydra is not typical of the Hydrozoa as a whole.’
    • ‘Traditional systematics divides the Hydrozoa into five orders.’
    • ‘While the Cubozoa always have polyp and medusa stages, either one can be reduced in the Hydrozoa and Scyphozoa.’


Modern Latin (plural), from hydro-‘water’ + Greek zōion ‘animal’.