The prophylactic nap is a nap taken ahead of a period of anticipated sleep deprivation, such as a late night or a long journey.预防性小睡是指在熬夜、长途旅行等影响睡眠的事情之前的小睡。I had a late night last night.我昨天晚上睡得很晚。We're tired today because we had a late night last night.今天我们累了，因为昨晚熬夜到很晚。