day是可数名词 但是有些地方就不能加s 所以就有些区别。
days
n.一天;一日;白昼;白天;工作日;一天的活动时间
day的复数
例句
How many days did you take off?
你休了几天假？
Installation of the new system will take several days.
新系统的安装需要几天时间。
I would imagine the job will take about two days.
我猜想这工作大概需要两天左右的时间吧。
It\'s been one of those days!
这一天真倒霉！
