A strut, or strut assembly, is a component of the suspension system used on most passenger vehicles today. Struts (often referred to as MacPherson struts, named for their inventor) are used with independent suspensions, as opposed to cars and trucks that have a straight axle or double wishbone suspension and rely on a set of leaf or coil springs and shock absorbers.
A strut is made up of a strut body, a coil spring, and a dampening device similar to a shock absorber. All of these components are tied together in a single assembly with a rotating plate at the top (the upper strut mount). This arrangement allows the top of the strut to act as the upper pivot point for the suspension.