sleep
1.sleep（名词）统指睡眠，a sleep指“一段时间的睡眠”，但很少用sleeps来指“多段时间的睡眠”。如可以说Sleep is necessary to health和He had only a brief sleep last night，但很少说I have had only brief sleeps during the past few weeks。
2.go to sleep是“入睡”，不是“就寝”，说“就寝”该说go to bed。例如：I usually go to bed at nine o'clock and go to sleep ten minutes afterwards. 一个人有时并不“就寝”也会“入睡”。例如：The baby went to sleep in the nurse's arms.
3.sleep（动词）通常作“睡眠”解，如I sleep for eight hours和He sleeps from nine at night to five in the morning。有时用作“入睡”解。例如：It is time to sleep. 但说“入睡”通常说go to sleep或fall asleep，不说sleep，如通常不说I slept at half past ten last night或As he was very tired, he slept as soon as he sat down，该把slept改作went to sleep或fell asleep。fall asleep通常含有“不想入睡而入睡”的意思。
4.sleep late不是“（晚上）睡得迟”而是“（早上）醒得晚”（日上三竿才醒）。
