A definition is where you say what something means. Or is it?
Is where. What an unuseful, unsatisfying phrase. I’m talking about definitions like these:
- A gravy train is where someone makes lots of money without doing much for it.
- A retweet is where you forward a tweet.
- Horticulture is where people grow plants.
If you wanted to understand gravy trains, retweets, and horticulture, these half-clarifications would leave you wondering what types of things these things are. Surely a gravy train has nothing to do with gravy or trains, does it? What exactly is a retweet before it gets forwarded? If horticulture is where people grow plants, does that make it a plot of ground? You might reread the definitions, suspecting that you missed something. You might feel vaguely cheated, left behind with the most basic of questions unanswered.
Is where. What a great big abandoner.
I say, abandon it right back. Here’s how. Whenever you’re struggling to define something, think Noun is noun. The first noun is the thing you want to define. The second is the category it belongs to: the type of thing the thing is.
- A gravy train is a source of income that …
- A retweet is a Twitter message that …
- Horticulture is the science of …
From there, you can go long or short with your definition, depending on what you think your readers will wonder about. You might explain what the thing does, how it works, what parts it comprises. You might include images, analyze word origins, give examples. Or you might not. But don’t skip over that categorizing noun. A definition is a statement that tells what type of thing a thing is. At least that is where, yes is where, a definition starts.
 I owe the phrase Noun is noun to Penny Jessie Beebe and Sharon Ahlers. During their many years of teaching Engineering Communications at Cornell University, they have passed along this tip to hundreds of students—and to at least one fellow teacher, who has now passed it along to you. After reading this post, Penny e-mailed to say, “The X is Y definition is one of the most useful tools I know for pressing students to pin down what they’re trying to explain. The companion to ‘noun is noun,’ of course, is ‘to verb is to verb.’ (When students need a definition of ‘verb,’ my version is ‘anything you can do, visible or invisible,’ and a noun is any thing, abstract or concrete.) ‘Adjective is adjective’ doesn’t work nearly as well because of the various suffixes, but I use it.”
 For definition examples of all kinds, see Mike Markel, “Drafting and Revising Definitions and Descriptions” in Technical Communication, 6th ed. (Boston: Bedford/St. Martin’s, 2002), 219–249.Google+