构词法是合成词，合成词mon+词根day，中文意思是n. 星期一

例如

It was a Monday， so she was at home.那是个星期一，所以她在家。

We only work from Monday to Friday.我们仅从星期一工作到星期五。

I'm going in for my op on Monday.星期一我要住院动手术。