forty

四十

Twenty plus twenty equals forty.

二十加二十等于四十。

四十几岁、四十多岁常用复数 forties

She started learning the piano in her forties.

她四十几岁才开始学钢琴。

四十年代常用复数 the forties

The photograph was taken in the forties.

这张照片是在四十年代拍的。

四十的、四十个

Forty students signed up for the summer course.

有四十名学生报名参加暑期课程。