Digital Video: A variable focal-length lens, used to magnify the target image. The most common zoom lens on digital cameras has a 3:1 ratio. The zoom function on digital cameras will be either an optical zoom or a digital zoom.
A lens having internal movable elements that allow the focal length to be changed without changing the image plane.
A lens with a variable focal length - usually which can be moved from a wideangle setting to a telephoto one - found on cameras and projectors.