( circadian ( ( rhythm ( ( A ( regular change ) ) ( in ( ( physiological function ) ( occurring ( in ( approximately ( 24-hour cycles ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN circadian)) (VP (VBZ rhythm) (NP (NP (DT A) (JJ regular) (NN change)) (PP (IN in) (NP (NP (JJ physiological) (NN function)) (VP (VBG occurring) (PP (IN in) (NP (RB approximately) (JJ 24-hour) (NNS cycles)))))))) (. .)))
circadian rhythm A regular change in physiological function occurring in approximately 24-hour cycles.
(ROOT (S (NP (NP (JJ Regular) (NNS changes)) (PP (IN in) (NP (NN biology) (CC or) (NN behavior))) (SBAR (WHNP (WDT that)) (S (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 24) (NN hour) (NN cycle))))))) (VP (VBP are) (NP (NP (NN part)) (PP (IN of) (NP (DT the) (NN circadian) (NN rhythm))))) (. .)))