Standard Lemma guide

circadian

adj · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.

  • UK: /səˈkeɪ.dɪ.ən/
  • Southern-England: Recorded audio is listed in the source snapshot.
  • US: /sɚˈkeɪ.di.ən/
  • US: /sɚˈkæd.i.ən/
  • US: /ˌsɝ.kəˈdi.ən/
  • US: /ˌsɝ.kəˈdaɪ.ən/
  • CMU ARPABET: S ER0 K EY1 D IY0 AH0 N Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.

1

adj

Meaning 1

Of, relating to, or showing rhythmic behaviour with a period of approximately 24 hours; especially of a biological process.

Definition source: English Wiktionary via Wiktextract

Usage: not-comparable

Topics: biology, natural-sciences

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: hemeral, nyctohemeral, diurnal, quotidian, circadian, daily, nychthemeral, per diem

Antonyms: none provided

2

adjective

Meaning 2

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

Definition source: Princeton WordNet 3.0

Examples

  • circadian rhythms

Meaning relationships

Synonyms: none provided

Antonyms: none provided

History

Etymology

Etymology 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”) + diēs (“day”) + English -an. Compare circannual.

Across languages

Translations

20 source translations are retained for this English entry.

  • Catalan: circadiari — relating to rhythmic behavior with a period of 24 hours
  • French: circadien — relating to rhythmic behavior with a period of 24 hours
  • Galician: circadiano — relating to rhythmic behavior with a period of 24 hours
  • German: circadian — relating to rhythmic behavior with a period of 24 hours
  • German: zirkadian — relating to rhythmic behavior with a period of 24 hours
  • Greek: κιρκάδιος (kirkádios) — relating to rhythmic behavior with a period of 24 hours
  • Icelandic: dægur- — relating to rhythmic behavior with a period of 24 hours
  • Icelandic: sólarhrings- — relating to rhythmic behavior with a period of 24 hours
  • Irish: laethúil — relating to rhythmic behavior with a period of 24 hours
  • Italian: circadiano — relating to rhythmic behavior with a period of 24 hours
  • Japanese: 晦日 (kaijitsu) — relating to rhythmic behavior with a period of 24 hours
  • Polish: całodobowy — relating to rhythmic behavior with a period of 24 hours
  • Polish: dwudziestoczterogodzinny — relating to rhythmic behavior with a period of 24 hours
  • Russian: циркадный (cirkadnyj) — relating to rhythmic behavior with a period of 24 hours
  • Russian: циркадианный (cirkadiannyj) — relating to rhythmic behavior with a period of 24 hours
  • Slovak: denný — relating to rhythmic behavior with a period of 24 hours
  • Slovak: cirkadiálny — relating to rhythmic behavior with a period of 24 hours
  • Slovak: cirkadiánny — relating to rhythmic behavior with a period of 24 hours
  • Spanish: circadiano — relating to rhythmic behavior with a period of 24 hours
  • Ukrainian: цирка́дний (cyrkádnyj) — relating to rhythmic behavior with a period of 24 hours
Real reading context

circadian in complete knowledge articles