Then he turned on his side and went back to sleep. 中为什么用side,表示什么意思啊

问题描述:

Then he turned on his side and went back to sleep. 中为什么用side,表示什么意思啊

turn on one's side 固定短语," 侧过身去,翻个身"
句意:然后,他翻了个身,又继续睡觉.