ˌdī(ˌ)ərˈnāshən noun
( -s )
Etymology: Latin diurn us of the day, daily + English -ation (as in hibernation ) — more at journal
1. : the habit of sleeping or being quiescent by day
the diurnation of bats
2. : a daily recurrent fluctuation in an ecological community (as the vertical movement of plankton)