nycthemeral
/nɪkˈθɛm(ə)rəl/ /nɪkˈθɛm(ə)r(ə)l/(also nychthemeral) Chiefly Biology and Physiology
adjective
Designating or characterized by a variation that occurs in a period of twenty-four hours, especially corresponding to the contrast between day and night.
Origin
Early 20th century; earliest use found in Nature: a weekly journal of science. From nycthemer- + -al. Compare French nyctéméral, nycthéméral.