Complex sentence: Naps are most often taken as a response to drowsiness during wakingbiphasic or polyphasic sleep, where the latter terms also include longer periods of sleep in addition to one single period.
Split into simpler sentences: Naps are most often taken as a response to drowsiness during waking hours. A nap is a form of biphasic or polyphasic sleep, where the latter terms also include longer periods of sleep in addition to one single period.