Mnemonics—those mental hooks we use to help us remember things like names, birthdays, grocery lists—can be fun as well as useful.

They work well for remembering which word of a prickly pair we want—like the “E” link to stationery and letter. Or the “O” that helps us remember that the capitOl is a dOmed building. Or the one Lane uses to spell embarrass. She says “When I do something to embarrass myself, I turn Real Red and feel like an ASS.” The rrass hook gets us by the trouble-spot in the word.

One of my favorite mnemonics doesn’t have much to do with language, except that it’s a good example of how well mnemonics can work.

This one involves Pi (Π)—the Greek letter that mathematicians use to represent the relationship between two parts of a circle.

If you divide the circumference of a circle by the diameter, the number you come up with is called Pi. It’s a little more than three, and it’s a non-repeating decimal—that is, the numerals to the right of the decimal point go on and on without repeating. So we use simplified versions, maybe three and one-seventh, or 3.14. But if you want to remember a few more decimal places, here’s how.

Imagine a young boy who hasn’t studied for his math test, so he plays sick to stay home. But his worried mother insists on taking him to the doctor (who happens to be German). When the boy sees a delicious-looking pie on the waiting-room table, he says: “May I have a piece?”

The doctor, who has seen many young malingerers, says “Nein. Too sick.”

Count the letters in each word of the child’s question, toss in a decimal point, and you’ll get 3.1415—the first numerals in Pi.

And the doctor’s reply—no counting needed—will give you the next three: 926.

After only one exposure to this little exchange, you’ll be able to recall—probably for months and maybe even years—that the first eight numerals in Pi are 3.1415926.

Even if you don’t personally care about remembering this particular bit of information, the exercise does show the power of mnemonics. And it’s an entertaining trick—one that you may want to teach to a child, or to a class. Or maybe you’ll just use it to show off a little with your friends.