Diel means something involving a 24-hour period that usually includes a day and the adjoining night.
Diel may also refer to:
Biology
Diel activity pattern, refers to the pattern of active times of an organism during a 24 hour cycle, such as Diurnal (active in the day), Nocturnal (active in the night), etc. Diel vertical migration, vertical migration is a pattern of 24 hours cyclic movement used by some organisms living in oceans and lakes.
People with the surname Diel Adrian Diel (1756–1839), German physician and founder of pomology Anton Diel (1898–1959), German politician Paul Diel (1893–1972), French psychologist Charles Diel, former head men's tennis coach, 1933-1942, for Louisiana State University Tigers
See also Diurnality Nocturnality Crepascular Matutinal Vespertine Cathemerality Diels, a surname Thiel (disambiguation), an etymologically related surname