Bolt

A bolt is a form of grooved fastener with an external helical male thread that engages the interior female thread of a nut. Bolts are closely related to, and often confused with, screws.
A screw is different from a bolt, because it does not take a nut, and its helical thread is used to penetrate (cut into) a softer material (such as wood).
This distinction is not always clear, and sometimes screws are regarded as bolts without a nut.