circadian

[Latin circā, around; see circa + Latin diēs, day.]

Denoting a period of about 24 hours.

• c. clock — the daily rhythm of physiological activity as expressed by the Chinese circadian clock. This explains the flow of energy or Qi through the body, via the meridians, each meridian having two hours of maximum and two of minimum function in every day.
• c. rhythm — the regular recurrence of certain phenomena in cycles of approximately 24 hours, e.g. biological activities that occur at about the same time each day (or night) regardless of constant darkness or other conditions of illumination.