screw

A screw is a specific kind of simple machine. The six classical simple machines are: lever, wheel-and-axle, pulley, inclined plane, wedge, and screw. A competent speaker readily calls a screw 'a simple machine.' This files against the nearest kind: simple-machine already contains lever, pulley, wedge, and inclined plane as accepted INSTANCE_OF edges.

The screw is a direct application of the inclined plane principle — an inclined plane wrapped around a cylinder. Which came first? The inclined plane as a concept predates the screw. The inclined plane fed into the design of the screw, making this a genuine derivation.

A screw IS a specific type of machine element — a cylindrical component with helical ridges that performs a specific function (fastening or motion conversion) within a machine or assembly. Per Law 9: a competent engineer would classify a screw as a machine element. This is compatible with its accepted DERIVED_FROM inclined-plane edge — the screw is an application of the inclined plane principle, implemented as a machine element.

Removal test (Laws 2b/8b): the screwdriver's accepted carve is 'engineered to rotate a screw fastener through a driven tip,' with tip geometry (flat, Phillips, Torx) matched to the screw head. Remove the screw and the mechanism has nothing to engage — the driven tip cannot perform its driving action and the tip geometries become meaningless; the tool ceases to operate as a screwdriver. Not purpose (8c): the screw is not what the screwdriver is FOR (that is the user's fastening task, which would be SERVES); the screw is the object the mechanism acts upon. Not identity: screw and screwdriver are distinct constructs with independent histories and uses (a screw fastens without a screwdriver present; a screwdriver drives without being a screw).