An Independent Suspension is an automobile suspension system that allows the wheels on an axle to move independent of each other. This is contrasted with a live axle or deDion system in which they are linked.
Most modern vehicles have independent suspensions on the front wheels at least. An Independent Rear Suspension (IRS), as the name implies, has the rear wheels independently sprung. A fully-independent suspension has an independent suspension on all wheels.
Early independent systems used swing axles, but modern systems have use Chapman or MacPherson struts, trailing arms, multiple links, or wishbones.
Another key difference which sets an independent layout from the conventional live axle, is that, for driven wheels, the differential unit does not form part of the unsprung elements of the suspension system. Instead it is either bolted directly to the vehicle's chassis, or more commonly to a subframe.
The characteristics of independant suspension
The relative movement between the wheels and the differential is achieved through the use of swinging driveshafts connected via universal (U) joints, analogous to the Constant Velocity (CV) joints used in front wheel drive vehicles.