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Formed as circ(a) +‎ annual, after circadian.


circannual (not comparable)

  1. (biology) Occurring or having cycles of approximately annual periodicity
    • 1956, USAF School of Aerospace Medicine, Report [80-114], [1956], page 11:
      […] because morbidity and mortality from cardiovascular disease also reveal statistically significant circadian and circannual rhythms.
    • 2000, Martin Hume Johnson, Barry J. Everitt, Essential Reproduction, page 110
      Circannual rhythms control reproductive function in seasonal breeders.
    • 2001, Joseph S. Takahashi, Fred W. Turek, Robert Y. Moore, Handbook of Behavioral Neurobiology, page 523
      Seasonal variations in locomotor activity are generated by a circannual clock […].