Antonyms of adj diurnal

2 senses of diurnal

Sense 1
diurnal (vs. nocturnal) -- (of or belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night"; "diurnal and nocturnal offices")

nocturnal (vs. diurnal) -- (belonging to or active during the night; "nocturnal animals are active at night"; "nocturnal plants have flowers that open at night and close by day")

Sense 2
diurnal -- (having a daily cycle or occurring every day; "diurnal rotation of the heavens")

INDIRECT (VIA periodic) -> aperiodic, nonperiodic -- (not recurring at regular intervals)

Similarity of adj diurnal

2 senses of diurnal

Sense 1
diurnal (vs. nocturnal) -- (of or belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night"; "diurnal and nocturnal offices")

Sense 2
diurnal -- (having a daily cycle or occurring every day; "diurnal rotation of the heavens")
       => periodic (vs. aperiodic), periodical -- (happening or recurring at regular intervals; "the periodic appearance of the seventeen-year locust")