It's difficult to collect dot tiles in mahjong.

He was collecting dots in mahjong.

This problem is very difficult.

I like to play mahjong with my friends on weekends.

What is this cylinder used for?

What is this tube used for?

The central part of a bicycle wheel is called a hub.

The child was playing in the park.

We need to gather the resources necessary to make the project successful.

We were able to gather everyone.