Marble is a type of very hard rock which feels cold when you touch it and which shines when it is cut and polished. Statues and parts of buildings are sometimes made of marble.

Marbles are sculptures made of marble.

Marbles is a children's game played with small balls, usually made of coloured glass. You roll a ball along the ground and try to hit an opponent's ball with it.

A marble is one of the small balls used in the game of marbles.

If you say that someone has lost their marbles, you mean that their ideas or behaviour are very strange, as if they have become insane.