English can be a very tricky language. Even when you look at words that are spelled using the exact same letters, a hyphen can completely change the meaning. “Recreation” refers to leisure activity, whereas “re-creation” refers to creating something again. And the deal with “second hand” and “second-hand” works in much the same way.

“Second hand” (with a space) refers to the hand on a clock indicating the number of seconds in the current minute. It’s a noun. The ticking sound of a clock comes from the second hand. Its corresponding partners on an analog clock are the hour hand and the minute hand, pointing toward the hour and minute, respectively.

“Second-hand” (with a hyphen) is an adjective, referring to an object that was previously owned by someone else. It’s something that is used or not new, as would be the case with furniture at a second-hand store or consignment shop. We often hear of second-hand smoke; the person with the cigarette has first-hand smoke. Everyone around him gets second-hand smoke.

It’s a term that is also used figuratively, as would be the case with second-hand knowledge or second-hand experience. If you didn’t actually experience something yourself and simply heard about it from someone else, you have second-hand experience.

“Secondhand” (as a single word) is an alternate spelling of “second-hand.” Whether you use the hyphen or combine the words together into a single compound word is a matter of convention and preference. While some resources, like Wikipedia, seem to prefer secondhand, a Google search for second-hand yields more results. Go figure. But both secondhand and second-hand are distinct from second hand.

So just as you should be mindful about whether to include a hyphen in “heads-up” and “cost-effective,” you may want to take a second to decide the right term to describe your used book.