Meaning

adjective of or relating to biological processes occurring at 24-hour intervals

originEtymology tree Proto-Indo-European *(s)ker-der. Ancient Greek κίρκος (kírkos)bor. Latin circus Latin circum Latin circā Proto-Indo-European *dyew- Proto-Indo-European *-s Proto-Indo-European *dyḗws Proto-Italic *djous Latin diēs Proto-Indo-European *-nós Proto-Italic *-nos Latin -nus Latin -ānus Old French -ainder. Middle English -an English -an English circadian From Latin circā (“around”) +…

Etymology from Wiktionary, CC BY-SA 3.0