Prime lens

A prime lens is a lens which has a fixed "zoom" or focal length. It is easier to make fixed focal lenses than to include them in a variable focus lens. Therefore, fixed focal lenses usually have a larger opening, known as an aperture, than comparable variable focus lenses. They are usually also of a higher optical quality.

Compact 85mm Canon prime lens with a maximum aperture of f/1.8

This Nikon 35mm wide-angle lens is a small, light-weight and "fast" prime lens with a maximum aperture of f/2