Definition of infradian in English:



  • (of a rhythm or cycle) having a period of recurrence longer than a day; occurring less than once a day.

    Compare with ultradian

    ‘The crayfish Procambarus clarkii is a nocturnal organism that displays a span of overt circadian and infradian rhythms to adapt to daily and seasonal environmental lighting changes.’
    • ‘The circadian rhythm resides with an infradian rhythm of lunar 28-day cycles, seasonal cycles of cold and hot as well as shifting light and dark.’
    • ‘In this paper, a presumptive role for infradian hormonal rhythms is considered.’
    • ‘Circadian and circannual rhythms of sex steroids in men have been well described, but infradian dynamics of estradiol and progesterone in men are unknown.’



/inˈfrādēən/ /ɪnˈfreɪdiən/


1960s from infra- ‘below’ (i.e. expressing a lower frequency), on the pattern of circadian.