I think you can generally classify Asperger's as a type of High Functioning Austism (HFA), but it's a very specific type of HFA usually marked by poor social skills, advanced and overly formal language, and extensive, pervasive interest in a specific subject (like dinosaurs, or train schedules, or insects, etc.). Those with Asperger's are often called "little professors" because of how much they know about a narrow range of interests, and how formal and intellectual their conversation seems.Those with HFA also have the poor social skills and sometimes the fixed, perseverating interests on a narrow subject matter common in Asperger's, but in contrast to those with Asperger's, they also usually have poor or underdeveloped language skills, too.The decreased inability to deal with change and/or the unexpected, and extreme sensory issues (i.e., either can't stand to be touched, or have no reaction to pain, claim loud noises hurt or gain a sense of calm from loud, rythmic banging, etc.) can be characteristics of either, so really, I think it's the language ability, or lack thereof, that marks the difference between someone with Asperger's v. someone with HFA.Hope this helps.