词性是名词,意思是:一天一日白昼 白天工作日一天的活动时间,例如:

1、The day should be mainly dry with sunny intervals.白天大部分时间应无雨,间有阳光。

2、They sleep by day and hunt by night.他们白天睡觉,夜晚捕猎。

3、He must be 70 if he's a day!他至少70岁了!