[Long-focus lens][1]:

> Optical designs of telephoto lenses must contain a telephoto group, which allows the lens to be physically shorter than its focal length. A lens with a conventional design and a focal length longer than a normal lens should properly be referred to as long focus.

And from [wikipedia][2]:

> A telephoto lens works by having the outermost (i.e. light gathering) element of a much shorter focal length than the equivalent long-focus lens ...

Non-telephoto long-focus lenses aren't used much anymore, at least in the SLR world, so you can basically just use telephoto to refer to longer focal lengths and not have to worry.

  [1]: http://photography.wikia.com/wiki/Telephoto_Lens
  [2]: http://en.wikipedia.org/wiki/Telephoto_lens