"Friendly AI" or "FAI" is an old term invented by Yudkowsky to mean an advanced AI successfully aligned with some [ idealized] version of humane values, such as e.g. [ extrapolated volition]. In current use it has mild connotations of significant self-sovereignty and/or being able to identify desirable strategic-level consequences for itself, since this is the scenario Yudkowsky originally envisioned. An "UnFriendly AI" or "UFAI" means one that's specifically not targeting humane objectives, e.g. a paperclip maximizer. (Note this does mean there are some things that are neither UFAIs or FAIs, like a Genie that only considers short-term objectives, or for that matter, a rock.)