A cantilever is a beam or structure that sticks out horizontally from a support, with only one end attached. Imagine holding a ruler flat off the edge of a table: the part hanging in the air, supported only where your hand holds it down, acts like a cantilever.

Cantilevers appear everywhere once you start noticing them. A diving board is a cantilever, anchored firmly at one end so it can spring from the other. Many balconies cantilever out from buildings, attached only at the wall. The wings of some airplanes use cantilever design, extending from the body without needing external wires or struts for support.

Engineers love cantilevers because they create dramatic, useful spaces without needing columns or supports underneath. The famous Fallingwater house by Frank Lloyd Wright features bold cantilevers that make rooms seem to float over a waterfall. Bridges sometimes use cantilever sections that reach out from both sides of a river until they meet in the middle.

The key to a cantilever is balance: the attached end must be strong enough to support the projecting part. Think of it like a seesaw where one side is bolted down. The word can also work as a verb: an architect might cantilever a roof to create a covered porch without blocking the view with posts.