On vs. About: The Definitive Answer?

Posted By on June 9, 2012

Cynthia and Emily holding two signs, one says "on," the other says "about"

On vs. about? Emily and Cynthia rowed on a shell about Lake Washington today and whined about rowing on and on.

I needed advice on a point of grammar. I couldn’t remember when to use “on” rather than “about.” I turned to the editor’s bible—The Chicago Manual of Style (CMOS), which handily is now online.

I posted my question in the CMOS Online forum and waited. A day later, an editor asked me for an example of a sentence so as to better answer my question.

I asked about whether to use “on” or “about” in the following sentence:

She gave a lecture on recycled plastics [or about recycled plastics].

Lots of editors chimed in, but the answer from one editor (user name deannacl) made the most sense:

Use “on” or “about”; it just doesn’t matter. The meaning is perfectly clear either way. You could also say the same thing half a dozen other ways: She gave a lecture covering recycled plastics. She gave a lecture regarding recycled plastics. She gave a lecture explaining recycled plastics.

Now, if you really want to rev up this “on” versus “about” debate, try an illustration like this: “He gave a lecture on an aircraft carrier deck.” versus “He gave a lecture about an aircraft carrier deck.” Big difference there. Duck! Here comes the wing of an F-18 Super Hornet!

To which another editor (user name usertk) replied, “I once attended a lecture on the surface of Mars. ’Twas rather chilly.”

The definitive answer?

So what’s the answer to the question about when to “use” on vs. “about?” If the sentence means the same thing using either one, you get to choose. If the sentence means something silly, or downright hysterical, you’ve chosen the wrong one.

In other words, you need to evaluate which one to use within the context of the sentence, and then decide. For example, using “on” rather than “about” in my example sentence led to so many possible meanings that the editors had a hay day. In that case, I would have chosen “about.”

Bottom line: there is no definitive answer–as with so many questions about grammar and usage.