Stone can be used to build things, such as in this dry stone wall

A stone is a piece of rock. It is a mass of hard, compacted mineral. The word is often used to mean a small piece of rock.

The word "stone" also refers to natural rock as a material, especially a building material. Natural stones used as building material include granite, marble and sandstone. Manufactured, artificial products, such as concrete or clay bricks, are not stone.