Q. Chicago, APA, and other style guides for US English require a comma before the conjunction in a series of three or more items, per Strunk and White. However, in recent years I have increasingly seen US publications not follow this rule. (I find myself more and more often rechecking to see if these periodicals and books are British!) Has your staff also noticed this tendency? If so, do you have a professional opinion on the subject?

A. First, let’s note that Strunk & White recommend the serial comma (1918) per Chicago (1906), not the other way around; we were using it when White was still learning to read! And since it is commonly called the Oxford comma, it seems the British have been onto it for a while as well.

Second, the serial comma is optional; some mainstream style guides (such as the Associated Press) don’t use it. If you google “serial comma” or “Oxford comma,” you’ll see a lot of heavy weather from opinionated commenters, but there are times when using the comma (or omitting it) results in ambiguity, which is why it’s best to stay flexible.