zeitgeber

American  

[tsahyt-gey-ber] / ˈtsaɪtˌgeɪ bər /

noun

1. an environmental cue, as the length of daylight or the degree of temperature, that helps to regulate the cycles of an organism's biological clock.

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Etymology

Origin of zeitgeber

First recorded in 1970–75; from German (1954), literally, “time-giver,” on the model of Taktgeber “electronic synchronization device, timer, metronome”