This is Part 1 of a two-part article. Part 1 covers the differences between hyphens, en dashes, and em dashes, and how to use hyphens. Part 2 covers how to use en dashes and em dashes and how to create them in Microsoft Word.

Hyphens, en dashes, and em dashes are often misused. They can indeed be tricky, but knowing how to use them sets the professional writer or editor apart from those who aspire to be pros.

First, let’s consider this: what’s the difference between a hyphen and a dash? Simple. A hyphen joins words; a dash separates words or phrases. They are not interchangeable.

There are two types of dashes: en dashes and em dashes. An en dash is longer than a hyphen, and an em dash is longer than an en dash. Here’s what they look like:

Hyphen

-

en dash

–

em dash

—

Hyphens

Deciding when to use a hyphen can be like deciding which political candidate to support. That is, no matter what you decide, someone is sure to disagree with you. But here are some situations where hyphens are needed.

Everyone agrees that hyphens are needed when one adjective modifies another adjective, which in turn modifies a noun. These are called a compound adjective, phrasal adjective, or compound modifier. These phrases consist of two or more words that are understood as a single item.

One example is an energy-efficient house. In this phrase, energy efficient must be understood as one term. It can’t be just an energy house, nor can it be an efficient house. Those phrases make no sense, or at the very least change the meaning. In contrast, in the phrase a large, black vehicle, we could drop the large and still have a phrase that makes sense—a black vehicle. So that’s not a compound modifier and no hyphen is needed.

Here are two more examples:

     The Cuban Missile Crisis was an earth-shaking event.

     Police said the victim is a 5-year-old girl.

We need hyphens because we can’t write just a 5 girl or a year girl. We need the entire phrase; it’s understood as all one term.

Only use a hyphen in a compound modifier when it comes before a noun. If the modifier is after the noun, a hyphen is unnecessary.

     Police said the victim is a girl who is 5 years old.

When a compound modifier is split by another word, use a suspended hyphen.

     I plan to take a two- to three-week vacation.

There needs to be a space after the first hyphen.

Also note that there’s no hyphen between an adjective and the noun it modifies, not even if the adjective is a compound one.

     A made-for-TV documentary showed the horrors of World War II. (not made-for-TV-documentary)

Sometimes, however, adjectives that modify numbers or capitalized words need a hyphen.

     The Cuban Missile Crisis occurred in the mid-1900s.

     The Cuban Missile Crisis started in mid-October, 1962.

And yet, no hyphen is necessary in these cases:

     The Cuban Missile Crisis ended in late October, 1962.

     Easter takes place in early April this year.

Another exception is if the compound adjective contains an adverb ending in ly. No hyphen is necessary in the italicized phrase below.

     The option of every editor making up his own rules is an easily dismissed idea.

Also keep in mind that there are numerous terms or phrases that you won’t be sure of. Are hyphens needed in these sentences?

     Her life-style choices are different than mine.

     I bought a water-proof flashlight.

These examples are only a few of almost limitless possibilities. So, with the confusing, complicated, and even conflicting rules, as well as boundless potential phrases, how do you know when to use a hyphen?

Flip a coin.

I’m joking, of course.

Run an online search for the phrase in question, keeping in mind you may find differing opinions. Find a reliable site and follow its advice.

See Part 2 of “Should I use a hyphen, an en dash, or an em dash?” for tips on using en dashes and em dashes and how to create them in Microsoft Word.