cir·ca·di·an /sɝˈkediən/
  (a.)生理節奏的
  cir·ca·di·an /(ˌ)sɝˈkædɪən, ˈked; ˌsɝkəˈdaɪən, ˈdɪ-/ 形容詞
  晝夜節律的,(二十四小時)生理節奏的,近日節律(的),一晝夜的
  circadian
       adj : of or relating to biological processes occurring at 24-hour
             intervals; "circadian rhythms"