while reading my british harry potter books we've discovered that the words study and revise are used almost interchangeably. we (myself, my husband, and my parents-in-law) have never seen this use of the word revise. it seems that revise may have more to do with preparing for a final exam and studying is the more all-purpous word, though at one point both are used in the same sentence. my dictionary does not elucidate. (the american version of the book uses study exclusively)

what, if any difference is there between the two words?