"BUT" is a coordinating conjunction--it joins 2 independent clauses and merely expresses the relationship (of contrast) between them
"HOWEVER" is a conjunctive adverb and "belongs" more to--or primarily modifies--the second independent clause.
The difference is so linguistically subtle, though, that it's easier to just memorize the rule that "however,"when used to join two independent clauses, needs to be preceded by a SEMICOLON and followed by a comma.
Periodically in the Writing Center we get clients who bring in papers that have some grammatical error that, for whatever reason (generally because the sentence is awful) that is difficult to explain. We've taken to writing these sentences down in our "Grammar Questions" book (colloquially known as the "Book of Shame"), and then the Grammar Fairy (who I have a sneaking suspicion is actually Jenn Lutman) writes a response in the book explaining how to correct the sentence and we usually discuss it at our next staff meeting.
ReplyDeleteThis particular Grammar Fairy response was to a question I posted about explaining to a client the difference between "but" and "however," since I intuitively know when to use one or the other but had no idea how to explain it to someone else beyond "this is correct because I say so." The response humored me with its illustration of the ridiculous technicalities of the English language.