Some people refer to CD singles as EPs as well. It's really a question of taste. Personally, I prefer to call those shorter, "single-length" recordings EPs only if they lack a defining track.
For instance, the Chemical Brothers' "Loops of Fury EP" is the only release to contain the letters EP in its title. The case is also made of white plastic instead of the usual black. This qualifies as an EP because all 4 tracks are different (read, not remixes of each other). Indeed, this release does not identify with any one album. You see, two of the tracks, Loops of Fury and These Beats Were Made For Breakin', appear on no album. Differing mixes of the other two tracks, "Chemical Beats (Dave Clarke Remix)" and the full version of "Get Up On It Like This", appear on two different albums, respectively Exit Planet Dust and Dig Your Own Hole.