You can start a sentence with "however," but you need to be careful. And what about "and" and "but"?
How to Use Semicolons with "However"
If you want to avoid starting a sentence with however, it's not hard to do—just grab a semicolon and use it to connect your two main clauses. What I mean is that instead of putting a period at the end of the sentence before the however, put a semicolon there instead.
For example, let’s take this sentence from Robert Pirsig’s introduction to the book Zen and The Art of Motorcycle Maintenance: “What follows is based on actual occurrences. However, it should in no way be associated with that great body of factual information relating to orthodox Zen Buddhist practice.” He just as easily could have put a semicolon in place of the period and written, “What follows is based on actual occurrences; however, it should in no way be associated with that great body of factual information relating to orthodox Zen Buddhist practice.”
Voilà. With the semicolon, you no longer have a however at the beginning of a sentence.
Conjunctive Adverbs and Semicolons
You put a semicolon before other conjunctive adverbs when they connect main clauses too. For example, you’d put a semicolon before the words consequently, moreover, nevertheless, still, and therefore in similar sentences. They’d each be followed by a comma too.
- It rained; consequently, the party was canceled.
- You have to come to the party. I bought balloons; moreover, I bought cake.
- I don’t trust him; nevertheless, we still have to work together.
- The house seems expensive; still, it’s the cheapest house available right now.
- I hate marshmallows; therefore, I hate s’mores.