chalk

Chalk is a soft, white, powder-like limestone.

Example: The men mine chalk in the hills near my house.

Chalk is a piece of chalk, or more usually, processed compressed chalk, that is used for drawing and for writing on a blackboard; teachers at school may use chalk to write on a blackboard.

Example: John wrote his name on the blackboard with chalk.

To put chalk on something, such as the tip of a billiards cue.

To write something using chalk; this is often done on a blackboard.

To use powdered chalk to put the lines on a sports field.