As a writer, I try to notice the obvious. There’s no reason to pay attention to the familiar, so to observe the obvious requires intense attention.

For that reason, one thing I love about studying a new subject is learning its particularized vocabulary. New words describing new concepts allow me to understand the world in a deeper way.

I remember one of the first times I realized how much more clearly I could think if I had a term for a complex idea.

I was in my first year of law school, and for the first time, I heard the term “opportunity cost.”

“Opportunity cost” is an economic concept that refers to the potential benefit or value that’s given up when one alternative is chosen over another. In other words, to get the benefit of one opportunity, you also pay the cost of losing the other opportunities that you now can’t pursue.

We face opportunity cost every day: If I spend my vacation going to the beach, I won’t go camping. If I sign my children up for piano lessons, they won’t spend that time reading or playing soccer.

It’s a very useful concept to keep in mind, and it can be surprisingly hard to remember that these trade-offs exist. For instance, I remember someone saying to me, “I’m going to law school because I’ll be able to get a much better job when I graduate than I could get now.” And I said, “But remember, if you don’t go to law school, you’ll be working for three more years. So don’t compare the jobs you could get now to the jobs you could get after law school. Compare the jobs you could get with three more years of work to the jobs you could get after law school.” And truly, that had not occurred to him! That by going to law school, he’d be giving up those years of work.

In my writing, I strive to find terms to clarify ideas. I contrast finishers and openers, and simplicity-lovers and abundance-lovers. I’ve received so many emails from people about my distinction between abstainers and moderators—people who say, “It’s such a relief to know that this is a thing! Now that I know that I’m an abstainer and my sweetheart is a moderator, life makes so much more sense.”

Sometimes, a single word or phrase can help us see the world much more clearly.