Lens Mount
The fitting on an interchangeable-lens camera that the lens locks into; it decides which lenses can be used on that camera.
On this page 3 sections
Cameras that take interchangeable lenses have a mount on the front: a ring with electrical contacts that the lens twists into and locks onto. Each camera maker has its own mount, and some makers use more than one. A lens made for one mount does not fit a camera with a different mount unless an adapter joins them.
How it works
The mount holds the lens at an exact distance from the sensor, which is needed for a sharp image. Its electrical contacts carry power and signals between body and lens, so the camera can focus, set the aperture and apply stabilisation. The opening size and the distance to the sensor differ between mounts, which is why they are not interchangeable.
Where it applies
Mirrorless cameras and DSLRs have mounts. Compact cameras, action cameras and phones have fixed lenses, so they have no mount.
What it does not promise
The same mount name does not mean every lens works fully on every camera. Older lenses, lenses for a different sensor size and lenses used through an adapter can focus more slowly, lose some automatic features or need manual focus. Independent lens makers also make lenses for several mounts.