Dictionary.com
definitions

circadian

[sur-key-dee-uh n, -kad-ee-, sur-kuh-dee-uh n]
|
SEE MORE SYNONYMS FOR circadian ON THESAURUS.COM

adjective

noting or pertaining to rhythmic biological cycles recurring at approximately 24-hour intervals.

RELATED WORDS

regularly, often, periodic, constantly, regular, routine, everyday, day-to-day, ordinary, commonplace, common, quotidian, cyclic, diurnal

Origin of circadian

1955–60; < Latin circā about + di(ēs) day + -an
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for circadian

Contemporary Examples of circadian

British Dictionary definitions for circadian

circadian

adjective

of or relating to biological processes that occur regularly at about 24-hour intervals, even in the absence of periodicity in the environmentSee also biological clock

Word Origin for circadian

C20: from Latin circa about + diēs day
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for circadian
adj.

coined 1959 from Latin circa "about" (see circa) + diem, accusative singular of dies "day" (see diurnal). The original use is in circadian rhythm.

Online Etymology Dictionary, © 2010 Douglas Harper
Medicine definitions for circadian

circadian

[sər-kā′dē-ən, -kăd′ē-, sûr′kə-dī′ən, -dē′-]

adj.

Relating to biological variations or rhythms with a cycle of about 24 hours.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.