A cantilever is any structure supported at one point which carries a load at the other end. Examples are a dome crane, an overhanging roof, and an unsupported balcony.

The cantilever's support need not be at one end, but can be in the middle of its horizontal span. For example, a seesaw is a cantilever. Horizontal cantilevers often have a counterweight on the their other end, such as with a crane. An aircraft wing is an example of a horizontal cantilever, where the support is on the end of the wing, supported by the wind, and the plane is the weight supported by the beam (that is, the wing).

Cantilevers need not be horizontal. A flagpole stuck in the ground is a cantilever, where the force of the wind against both flag and pole is the load causing stress. (Notice that the force against a cantilever's beam need...