from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Biology Relating to or exhibiting approximately 24-hour periodicity.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. of, relating to, or showing rhythmic behaviour with a period of 24 hours; especially of a biological process
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of or relating to biological processes occurring at 24-hour intervals
Latin circā, around; see circa + Latin diēs, day.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin circā ("about") and diēs ("a day") with the English suffix -an. (Wiktionary)