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How to Use a Hyphen

Learn how to properly use hyphens with compound adjectives, and more.

By
Mignon Fogarty
December 14, 2012
Episode #347

The other day on Twitter, I wrote that I was using my noise-canceling headphones because the wind was so loud.

In response, Jessica Saint Jean asked if a hyphen should go between “noise” and “canceling.”

A hyphen would be OK there, because “noise” and “canceling” are acting as a compound modifier, modifying “headphones.”

Notice how I said it would be OK, and I didn’t use any strong words like “must hyphenate” or “should hyphenate”? Although there are a few hard-and-fast rules for using hyphens, there are just too many exceptions to call everything relating to hyphens a rule.

What Is a Hyphen?

Hyphens are a “look-it-up” punctuation mark. Though hyphens have several uses, we’re going to focus on how to use hyphens with compound adjectives. Compound adjectives are two or more words that together make an adjective. When they come directly before a noun, they’re known as compound modifiers and usually have a hyphen, like “noise-canceling headphones.” Here are a few more examples:

  • They had a long-term relationship.

  • The fire-proof vest proved to be a great life saver for Santa Claus.

 If the adjectives come after the noun, then they don’t need a hyphen. For example

  • Their relationship was long term. 

  • Santa’s new vest is fire proof.

     

Hyphens Can Change Meaning

Sometimes, the placement of a hyphen changes the meaning of your sentence. Let’s say you want a “hot-water bottle.” With a hyphen between “hot” and “water” you clearly want a water bottle for holding hot water because “hot” and “water” are joined by a hyphen. Without the hyphen between “hot” and “water, you might want a water bottle that is hot. See how the presence or absence of a hyphen could change the meaning?

The reason I didn’t say that I absolutely should have hyphenated “noise canceling headphones” is that if leaving out the hyphen causes no ambiguity, some style guides, such as the Chicago Manual of Style, say it’s OK to leave it out; and I don’t think anyone would read my meaning differently with or without a hyphen.

In the “hot water bottle” example, the difference is pretty subtle too. You probably don’t need the hyphen, but it’s not wrong to use it either because someone probably could be confused.

The more likelihood there is for confusion, the more you need a hyphen.

The Grammar Monkeys account on Twitter, run by the editors of The Wichita Eagle, often tweets examples of sentences they see where a missing hyphen makes a big and funny difference. Many of these are things they actually saw in news stories. Two of their recent “Why we need a hyphen” examples were as follows:

Prefixes and Hyphens

Some prefixes need hyphens, such as “re—,” “mid—,“ and “ex—.“ For example

  • My ex-boyfriend took the movies I enjoyed.

  • The mid-1990s were interesting.

  • Santa needed to re-read the Naughty or Nice list.

     

Using Hyphens with Ages

Several readers’ comments from a previous episode about hyphens had to do with numerals, including ages.

There’s a general rule: if the ages are being used as adjectives or nouns, use hyphens.

  • The five-year-old boy wanted the red balloon. (“Five-year-old” is hyphenated because it’s an adjective that modifies the noun “boy.”)

  • Rudolph is a two-year-old reindeer. (“Two-year-old” is hyphenated because it’s an adjective that modifies the noun “reindeer.”)

You can also use hyphens with implied nouns. For example, since you already know Rudolph is a reindeer, you could say “Rudolph is a two-year-old.” The hyphenated phrase “two-year-old” is essentially modifying the noun you left out: “reindeer.” You can also think of "two-year-old" as a noun--and nouns are usually hyphenated.

However, if the age comes after the noun (or after a noun and a verb, such as "Rudolph is" below), then it doesn’t need a hyphen because it isn't directly modifying the noun.

  • Rudolph is two years old.

  • Our pug is 12 years old.

Words or Numerals with Hyphens?

Many readers had questions about whether you write out numbers or use numerals with hyphens. It’s a style choice, so the best advice is to pick a style guide and stick to it. The Associated Press recommends using words for all numbers less than 10, and the Chicago Manual of Style recommends using words for all numbers less than 100, and their recommendations are no different when you’re using hyphens.

Therefore, if you’re using AP style, you’d write that Santa used a 15-foot sleigh (using the numeral 15), and if you’re using Chicago style, you’d write that Santa used a fifteen-foot sleigh, (writing out the word “fifteen”). Either way, you’d put a hyphen between “fifteen” and “foot” because it’s a compound modifier.

Other Uses for Hyphens

You also use hyphens

  • with prefixes that come before a word that needs a capital letter, like “anti-American”

  • when separating words with the same three letters in a row, such as “fall-like”

  • when writing numbers twenty-one through ninety-nine, such as

    • thirty-eight* 
    • ninety-nine
    • twenty-five
  • when joining letters and words, like “X-ray” and “A-frame”

     

Suspended Hyphens

You can also suspend hyphens. No, it doesn’t mean they got in trouble at grammar school, it means that to save space, you can suspend hyphens when you’re listing several words describing the same noun. How do you suspend them? Let’s say Santa found a fire-proof, dog-proof, and soot-proof vest online. You don’t need to write the full compound adjective each time, since each one is modifying the same noun, “vest.” Instead of writing “proof” each time, you’ll list them, each with only the first part of the compound, followed by a hyphen and then a comma. So if you were suspending hyphens when listing what type of vest Santa was planning on buying, you’d write that he purchased "the fire-, dog-, and soot-proof vest online."

If the rules aren’t confusing enough already, there are a few things that you should avoid or not do when using hyphens.

Stacked Modifiers

Although it’s OK to use hyphens with two or three adjectives to describe a noun, you shouldn’t overdo it. Using too many modifiers before a noun can complicate your sentence. Let’s look at a good example, followed by a not-so-good one:

  • The forty-year-old man looked like Santa Claus. (Good)

  • The uses-too-many-silly-hyphens-for-added-effect woman was Mrs. Claus! (Excessive)

Although the above example about Mrs. Claus would be OK on the rare occasion, as a general rule, when you’re being serious, you may want to consider three hyphenated modifiers before a noun as the limit.

Hyphens and Adverbs

Although it’s OK to use hyphens with adjectives, hyphens and adverbs don’t get along as well. You shouldn’t use hyphens with adverbs such as “happily” and “individually.” For example, you don’t put hyphens in phrases such as “happily married man” and “individually wrapped cheese.”

Summary

The quick and dirty tip for using hyphens is to check a dictionary or style guide.  If you don't have one handy, follow the rule that you hyphenate compound modifiers when they come before a noun, and don't hyphenate them when they come after a noun.

Web Bonus

A few years ago, the Associated Press removed the hyphen from “e-mail” but left the hyphen in “e-commerce” and “e-business.” You can see why hyphen rules are confusing! Over time, words can become open compounds, closed compounds, or even hyphenated compounds. “Coffeehouse” is a great example. I’ve seen it spelled three different ways: coffeehouse, coffee house, and coffee-house.

Thanks to Ashley Dodge for editorial assistance with this article.

*The original article listed "one-hundred" as an example, which is incorrect. "One hundred" does not take a hyphen.

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