An environmental agent or event that provides the cue for setting or resetting a biological clock. To be synchronized with our environment, we need the input of Zeitgebers. The most important Zeitgeber in nature is light. Social factors, chemical factors and activity can also serve as Zeitgebers. Light is a so-called photic type Zeitgeber, whereas [..]

noun. a cue, like the length of a day, utilized to initiate or time a biological rhythm.

Specific environmental variables that provide time cues (eg, light, food-availability cycles)

Literally, “time-giver” (in German). The stimulus (usually the light–dark cycle) that entrains circadian rhythms.

environmental time cue that entrains biological rhythms to a specific periodicity.  Known Zeitgebers are light, melatonin and physical activity.  To be effective, these signals must occur when the bio [..]