however

See although.

People disagree as to whether we should put however, meaning "nevertheless," "nonetheless," "but," at the beginning of new sentences. Therefore, it is wise to avoid it by combining two main, contrasting, clauses and linking them with however: He was indicted for the crime; however, he was acquitted by the jury at trial. Notice that a semicolon must precede however and a comma must follow it when two main clauses are linked like this. A common error is to set however off with commas, as in this incorrectly punctuated sentence: He was indicted for the crime, however, he was acquitted by the jury at trial.

When however in the senses mentioned here appears in the midst of a sentence expressing ideas contrasting with what has been said in a previous sentence, put one comma before however and another after it: The resort has closed for the season. Its staff members, however, are remaining on the property to service and repair the ski lifts. However can also appear at the end of such a sentence, punctuated by a single comma just before it: Its staff members are remaining on the property to service and repair the ski lifts, however.

However has other meanings, and those meanings dictate whether or not you punctuate the word and how. If you use however to mean "to whatever degree," "in whatever way," or "how" at the outset of an introductory main clause, put a comma after the clause, as in However hard it snowed during the night, the road crews were able to clear the main arteries before the rush hour. If however, meaning "in whatever way," modifies another adverb and the two appear as a pair in mid-sentence, put a comma before and after the two words: The coaching staff has begun, however reluctantly, to admit major flaws in the offensive team's tactics.

It is redundant to pair but with however. Use one word or the other, not both. Thus, this sentence is poor: The flight was initially canceled but it did manage to take off five hours late, however. Keep but and drop however.