Q: I’ve managed to get myself into a debate with my girlfriend that is now running to two weeks and threatening our relationship. The question is whether or not one should use a comma before the word “too” at the end of a sentence—e.g., “Steve likes chocolate ice cream too.” The Chicago Manual of Style says you shouldn’t, but my girlfriend has found a website that says you should. I’m no grammarian, but I’d appreciate something approaching a definitive answer. Can you help?
A: In the universe of yeses and noes, the comma-bef0re-“too” question is a maybe (which explains why two intelligent people can disagree about it). There’s no grammatical rule that says you must use a comma with “too” in the kind of sentence you describe. It’s largely optional, and depends on the inflection the writer intends. In the case of “too,” use a comma if you intend to be emphatic about it.
Take your example: “Steve likes chocolate ice cream too.” Context might call for a comma or it might not. If Grandma has just given Steve’s pushy little brother Sam a scoop of ice cream, and their mother wants to suggest that shy little Steve should get the same, she might say, “Steve likes chocolate ice cream, too.” (With a little lilt at the end, emphasizing the “too.”)
But if Mom is just describing a catalog of the stuff that Steve likes, and has already mentioned, say, vanilla ice cream, she might say, “Steve likes chocolate ice cream too.” (No particular inflection there.) It’s often a judgment call.
In the middle of a sentence, however, a comma before “too” can be a help to the reader.
[Update, Feb. 19, 2021: Since we published this post, almost 15 years ago, The Chicago Manual of Style (now in its 17th edition) has clarified its position. It now says (section 6.52): “The adverbs too and either used in the sense of ‘also’ generally need not be preceded by a comma.” One of the examples given: “Anders likes Beethoven; his sister does too.” It adds: “When too comes in the middle of a sentence or clause, however, a comma aids comprehension.” The example: “She, too, decided against the early showing.”]