What is a prime lens?
In the old days (you know last year), before digital, lenses that you could not zoom were referred to ask "fixed focal length lenses". A 50mm lens for instance is a fixed focal length lens. Sometime with in the last ten years or so the common vernacular has been to refer to these lenses as "Prime Lenses" perhaps be cause it's shorter? or perhaps because it just sounds sexier. But in the end they are the same. Our friends at Nikon are using the term "Single-Focal Length". Same thing.