A few days ago I had the pleasure of proofreading Issue 9 of your Young Scientists Journal, whose theme is nanotechnology and whose message is that “small is taking over the world” (as Muna Oli puts it in the conclusion to her excellent article). That message inspired me to write this blog, which is about one of Writing’s smallest, and most powerful, things: the hyphen.

   “Powerful”? Oh, yes indeed: it has the power to totally change the meaning of a statement, as the following examples illustrate.

        A: Police Help Dog Bite Victim.

        B: Police Help Dog-Bite Victim.

   In A (which actually appeared as a headline in an American newspaper in 1986), the absence of the hyphen means that the police helped the dog bite the victim (which conjures the hilarious image of a snarling police officer chomping on the poor chap’s ankle); in B, the presence of the hyphen means that the police helped the victim.

        C: She is an American football player.

        D: She is an American-football player.

   In C, her nationality is known (she’s American) but the sport is unclear (could be either soccer or US-style football). In D, thanks just to the hyphen, it’s the reverse: her nationality is unclear but the sport is known—US-style football. C could mean “She is an American soccer player,” and D could mean, “She is a Swedish player of American football,” or Thai or Tibetan or whatever.

   So the tiny hyphen is definitely powerful. It’s also versatile, having a wide range of functions. The hyphen breaks words at the ends of lines; it serves as the minus sign in mathematics; it’s used as a decency device, as in “sh-t”; and so on. But the hyphen’s primary (and most important) function is in compound modifiers. These are two words that jointly modify, or influence the meaning of, a third word, as in “award-winning scientist,” or “high-performance car,” or “yellow-bellied toad.”

   How do you know when you have a compound modifier—that is, how do you know when you need a hyphen? The dictionary usually doesn’t tell you, and SpellCheck is useless for hyphens—so what can you do? Here’s my personal trade secret for knowing when you need a hyphen in any trio of words: Mentally drop each of the first two, and if the meaning changes or becomes nonsensical, then you need a hyphen.

        yellow-bellied toad needs the hyphen because “yellow toad” is not true (only the belly is yellow) and “bellied toad” is nonsensical.

        high-performance car needs the hyphen because both “high car” and “performance car” are nonsensical.

        award-winning scientist: “award scientist” is nonsensical, “winning scientist” is true but inaccurate.

        US-style football: "US football" is accurate but "style football" is nonsensical.

        It was a young bald eagle: no hyphen is needed because both “It was a young eagle” and “It was a bald eagle” are still true and accurate.

        She ate low-fat food: “low food” is nonsensical and “fat food” entirely changes the meaning.

        She ate fresh health foods: both "She ate fresh foods" and "She ate health foods" are still true and accurate.

        He was a chemical-engineering student: “a chemical student” is nonsensical, “an engineering student” is true but vague.

   That last example raises the topic of style: while “He was a chemical-engineering student” is correct, it’s awkward. Much better to express the same thing as, “He was a student of chemical engineering.” In other words, sometimes it’s better stylistically to not use compound modifiers. I’ll devote a future Blog on Writing to just that, the very large and very important topic of style.