"Snabbt" and "fort" can sometimes be used as synonyms, but "fort" lays emphasis only on the speed, while "snabbt" signifies both the speed or the shortness of the event. "I'm not sure if "fort" is ever used as an adjective, whereas I think "snabb" can be used as an adverb. I'll have to give it some more thought apparently. But briefly: You would call a boxer that has very fast punches "snabb", not "fort". You would also characterize the punches as "snabba" and say that he punches "snabbt". The same would apply to a car I think, in the sense of "en snabb bil", yet you could say "bilen (föraren) körde för fort" as well as "för snabbt". http://forum.wordreference.com/threads/swedish-snabbt-vs-fort-synonyms.3002348/ "The words are mostly interchangeable, but there are a few differences. I do not know a general rule, but I can give you an example. There is a show by the comedian/linguist/author Fredrik Lindström called "Svenskar är också människor!". Theoretically, one could interpret the title in two ways. If read with the emphasis on också, it would translate to "Swedes are people, too!", meaning that Swedes are people or human beings just as much as other nationalities. If read with the emphasis on människor, it would rather mean that Swedes are also human beings besides being other things like mammals, Scandinavians, etc. In the given context, I think the first interpretation is the most natural. However, if one would replace också with även, "Svenskar är även människor!", then the second interpretation is the only possible (but would sound rather strange). In spoken Swedish, one would mostly use också. The word även is somewhat more formal and more often seen in written Swedish. Note that it also occurs in a slightly different meaning in the phrase även om (even though). The words likaså and tillika are seldom used and should be avoided by a person who is new to the language. " http://www.thelocal.se/discuss/index.php?showtopic=61407