Introductory Element Comma Rules Apply Regardless of a Leading Coordinate Conjunction
The Comma
Rulebase Summary
If an introductory element does not need a comma after it at the beginning of a sentence, do not add one just because the sentence starts with a coordinate conjunction. If an element does need a comma after it, still use the comma when the sentence begins with a coordinate conjunction. Elements that always require surrounding commas (direct address, parentheticals, interjections) should be surrounded after the coordinate conjunction as well.
Examples
A. And, yesterday he left without saying anything.
A. And yesterday he left without saying anything.
Short introductory modifier needs no comma — adding a conjunction doesn't change that.
A. But because there were computer issues I didn't get it.
A. But because there were computer issues, I didn't get it.
Introductory adverb clause needs a comma — the leading conjunction doesn't change that.
Transcript Notes
The presence of a coordinate conjunction at the beginning of a sentence does not change the comma rules for introductory elements. Apply the same punctuation rules you would use if the conjunction were not there. This also applies to the second part of a compound sentence after the conjunction.
Style Guide References (4)
BGGP
BGGP
BGGP
BGGP