Aperture

Aperture is a hole. Typically, it means the light opening in the lens of a camera. Most camera lenses have adjustable apertures. A large opening in the lens lets more light through than a small hole will. The ratio of the lens focal length to its aperture's diameter is called f-stop. Lenses call out the f-stop since that is the relative measure of the light coming through the lens to set the exposure. A small aperture (large f-stop ratio) will have a greater depth of field, and a large aperture (small f-stop ratio) has a shallower depth of field.