Is it correct to use BUT start a sentence?

According to standard American English grammar, "but" is not an acceptable Word to start a sentence with - it is a conjunction to be used in the middle of a sentence. However, in sloppy American useage, many people do start sentences with "but" when speaking. In general, you should avoid starting sentences with "but" unless there is a specific reason (such as colloquial dialogue).

Alternative Words for "but" at the start of the sentence include "however", "alternatively", "conversely" and "nevertheless". These are adverbs and are acceptable beginning Words.