In machine construction, a usually circular cylindrical member with a continuous spiral rib or thread, used either as a fastener or as a force and motion modifier. Various types of screws are used to clamp machine parts together. Wood screws are made in a wide variety of diameters and lengths; when using wood screws, small starting holes called pilot holes are often drilled first to avoid splitting the wood. Screws that modify force and motion are known as power screws. The screw is considered one of the five simple machines. See also wedge.

This entry comes from Encyclopædia Britannica Concise.
For the full entry on screw, visit

Seen & Heard

What made you look up screw? Please tell us what you were reading, watching or discussing that led you here.