A mast is a narrow structure, usually composed of beams, which is designed to hold something up at a high point. Masts generally do not enclose any interior space, although they may hold a ladder inside a framework or a hollow space inside a pole.

The slender structure raises a supported item rather than providing occupied floors. A ladder or a hollow pole interior does not amount to a regular occupied interior.

Masts can use a single pole, an open framework, or lateral guy wires. The supporting arrangement distinguishes those more specific mast forms.