Definition from Wiktionary, the free dictionary
circannual (not comparable)
- (biology) Occurring or having cycles of approximately annual periodicity
1956, USAF School of Aerospace Medicine, Report [80-114], , 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 […].
In practice circannual is not used comparatively. In principle, one biorhythm could be "more circannual" than another if its period were closer to a year than the other's.