English is all English, isn’t it? Does it really matter how you place the apostrophe or comma? Yes, it does. There are a ton of style guides writers and editors use to govern what goes where and how it appears. There’s MLA, AP, APA, AMA–seriously, the list goes on.
For our purposes, we’ll focus on the most common two: Associated Press Style (AP)–used mainly for PR and journalistic purposes–and the Chicago Manual of Style (CMOS) used for books, periodicals, and journals.