Printable Version
Pronunciation: sêr-kay-di-yên Hear it!

Part of Speech: Adjective

Meaning: Related to a 24-hour cycle, around-the-clock.

Notes: Today's Good Word has an adverb, circadianly, but no noun that I know of. We will have to settle for the phrase solar day with its diurnal and nocturnal sides. Russian has a noun for "day" in the sense we use our word: den'. It also has a word for a 24-hour day, sutki. So do other languages, like Polish dzień and doba, and Swedish dag and dygn. English seems to lack this distinction.

In Play: Let's try today's Good Word with the noun it is most often associated with: "Herb found that working the night shift challenged his natural circadian rhythm." Circadian cycles take on a mystic meaning for some: "Lucinda Head wears sunglasses during her waking hours because she thinks that ultraviolet light interferes with her circadian rhythms."

Word History: Today's Good Word was introduced in a 1959 article by F. Halberg referring to "circadian rhythms" in animals. He created the word form Latin circa "around" + dies "day". Latin circa is from circum "around", based on circus "circle". Circus comes from Proto-Indo-European (s)ker-/(s)kor- "turn, bend", with a Fickle S, which is sometimes there and sometimes not. We find the PIE root in these English borrowings from Latin: circle, the prefix circum-, and, of course the three-ring circus. Latin dies comes from a PIE word that has blossomed into words with different, though related, meanings: "day", "sky", "god" and "heaven". English borrowed several of these derivations from Latin, including deity and divine. Journey comes via Old French journee "a day's work or travel" from Latin diurnus "of a day". (Our gratitude to Kathy McCune, now of Sweden, is circadian, because of such recommendations as today's useful and beautiful Good Word.)

Dr. Goodword,

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