His forehead is very prominent.

This mirror is convex in shape.

Her forehead is very attractive.

This mirror is made with a convex lens.

We need to think about this problem in multiple dimensions.

This problem is simple, so it can be solved quickly.

This problem is simple, so it can be solved quickly.

My family consists of four people.

I drew a four in mahjong.

We are all part of the same brethren.