The photographic lens has a specific ‘mount’ arrangement on the end of the lens body. The mount is the mechanical fitting that marries the lens body onto the camera, locking it in the correct position for use. It is a mechanical lock of a design unique to a specific type of camera. Camera brands usually have their own mount system (eg. Canon lens mount only fits Canon cameras). Different lens mounts are not interchangeable.
In modern cameras (DSLRs and some SLRs), the mount may also complete an electrical interface. A system of electrical contacts click into place when the lens mount locks. The completed circuits allow for the various motors and sensors in the lens to be controlled from the camera body.
Individual lenses are only usable on certain cameras. Manufacturers normally ensure that the fitting of incompatible lenses is prevented by specific mount design. Information for individual lenses and mounts will be found in the data for the lens in question. Check that the mount and lens you want to use is suitable for your camera model before you purchase a lens. Links to lens manufacturers are given below.
Mounts are only fitted to lens bodies that are interchangeable. Allowing the use of a variety of compatible lenses to be fitted as required to the camera body. Interchangeable lenses with mounts are normally only fitted to DSLRs (and formally to SLRs).
Mounts can be of a range of mechanical or screw fitting types depending on the make and type of camera. However, most have a pin or bayonet locking mechanism which prevents premature or accidental release of the lens body from the camera.
“That lens will only mount on a Nikon camera”.
Only lenses suitable for Canon Cameras have the Canon mount system.