Usage and Grammar

Q. Hello: I am working on writing and editing thank-you letters to faculty and staff participants in a curriculum session for third-year medical students. Should I treat “data” as a singular or a plural noun? I have been looking for a definitive answer to this question in online style manuals and grammar guides. If its answer is already in the CMOS and you could refer me to the appropriate part of the website where this information is posted, that would be excellent.

A. If you type “data” into the search box on the CMOS web page, it will give you several places where the word is discussed in our Q&A, and you’ll see that it can be either singular or plural. For questions like this, however, I find that a dictionary is a very helpful tool. Judging from the number of queries we receive asking about the meaning or usage of particular words, it seems that people rarely think of using a dictionary, which is surprising, considering that it is much quicker to look up a word than to search through style manuals—or type a question to an online advice column. There are even online dictionaries, if turning paper pages seems too old-fashioned or too big a nuisance. In honor of your question, I’m tempted to create a new category of Q&A column called “You Could Look It Up” (in the hopes that readers will take the hint).