This post, dear reader, describes proper punctuation and capitalization associated with writing in which one or more people are being addressed by name or role.
Confusion abounds about how or whether to set off a proper or common noun that serves as a label for one or more people from a statement directed at that audience, and when to capitalize the first letter of an otherwise lowercased word that serves that function.
One of the outcomes of the trend toward less formal correspondence is the tendency of writers to omit punctuation from salutations, as in “Hi Buffy!” Technically, the greeting should read, “Hi, Buffy!” I can’t police Muffy’s every missive to Buffy, but at the risk of sounding stuffy — and making Muffy huffy — I’ll remind her (and everyone else) of that fact in this public forum. (However, because dear in “Dear Buffy” is a modifier, not an interjection, that phrase receives no punctuation.)
Another locution that, by the ubiquity of erroneous usage, increases such errors virally is the incorrectly comma-free truncation of “May I have your attention, shoppers” and the like: “Attention shoppers.” The word shoppers is a form of direct address and must therefore be set off from the preceding interjection by a comma.
A comma should, likewise, be inserted after the direct address in “Ladies and gentlemen start your engines,” which otherwise reads as if the statement means that well-bred women and men provide the service of turning the readers’ ignition keys.
Whenever a sentence communicates that one or more people are being spoken to, a comma (or two) is part of the process. When the term of address precedes the statement, insert a comma after the term of address: “Sir, please follow me.” When the term of address follows the statement, insert a comma before the term of address: “Good job, everybody.” When the term of address is inserted into the statement, brace it with two commas: “Please, miss, can you tell me the time?”
But note that these terms of address do not begin with uppercase letters. When are such terms capitalized? This emphasis is generally provided only when the term is a substitution for a known name: “What do you suggest, Doctor?” “Please tell us, Senator, how you came to that conclusion.”
This rule applies to designations of family relationships, too: “Can I go see a movie, Mom?” (Or “I asked Mom if I could go see a movie.” But “I asked my mom if I could go see a movie,” because, in this case, you’re merely describing the person — “my mom” — not naming her.)