• 5-minute read
• 4th December 2019

Writing Tips: What Are Compound Words?

Not every word in English needs to stand alone. Sometimes, words like to join up. And these compound words may have a completely new meaning. But how can you avoid errors when using these terms? Join us for a look at open, hyphenated, and closed compound words.

What Are Compound Words?

Compound words are made up of two or more other words. They can be written as open compounds, hyphenated compounds, or closed compounds:

• Open compounds are written as separate words, but they are conventionally used together (e.g., full moon, mobile phone, ice cream).
• Hyphenated compounds occur when two or more terms are joined with a hyphen (e.g., mother-in-law, well-known, T-shirt).
• Closed compounds are written as a single term but combine two or more words that could be written separately (e.g., notebook, boyfriend, childlike).

The question is often what type of compound word you need to use!

Open, Hyphenated, or Closed?

As explained above, compound words come in three kinds. Which type of compound to use is often a matter of convention, so if you’re not sure whether a word should be open, hyphenated, or closed, you can look it up in a reliable dictionary to see how they spell it.

With some words, though, you have more than one option. “Email,” for example, can also be written as “e-mail,” and “car pool” can be spelled “carpool.” In these cases, our main tip is to use one spelling consistently throughout the document you’re writing. And if you are using a style guide, you may want to check if it specifies how to write compound words.

In addition, we have a few tips for when to hyphenate compound words.

When to Hyphenate Compound Words

The rules about hyphenating compound words are fairly flexible, but they can be useful. The most common guidelines are to hyphenate:

• When using a compound modifier before the word it modifies (e.g., a well-laid plan or a mind-numbingly boring speech).
• When writing compound numbers between twenty-one and ninety-nine.
• With ages and time spans in years (e.g., a seven-year itch).

However, you would not usually hyphenate compound adjectives when the first term is either “very” or an adverb ending in “-ly.” For example:

She found a perfectly formed gemstone. ✓

She found a perfectly-formed gemstone. ✗

Nor would you usually hyphenate compound adjectives when they come after the noun they modify. For instance:

The plan was well meaning. ✓

The plan was well-meaning. ✗

Again, there’s some variation here (e.g., “old-fashioned” is almost always hyphenated, even when it appears after the term it modifies). But, as long as you’re consistent and you remember to check a dictionary if you’re unsure about a word, you should be able to avoid errors.

One Word or Two?

Compound words often have meanings that differ from their constituent parts. This makes it easy to accidentally use a compound when you really need two separate words. “Everyday,” for example, is an adjective meaning “ordinary” or “routine.” It should be used like this:

My everyday clothes were in the wash, so I wore pajamas to the pub.

This isn’t the same as “every day,” which is written as two words and means “each day.” As such, it’s important not to get these terms confused if you want to be clear about what you mean. Remember:

I go to the pub every day. ✓

I go to the pub everyday. ✗

Similar terms include “already” and “altogether,” which have distinct meanings from “all ready” and “all together.” It’s often worth thinking about whether you really need a compound word, or whether you really need two terms.

Nouns and Verb Phrases

One tip that can help is considering whether a compound word is being used as a noun or a verb phrase. Typically, the noun forms are written as a single closed compound. For instance, “set” and “up” become “setup”:

My computer setup cost me thousands of dollars.

Here, for example, “setup” is one word because it refers to a thing, not an action. The verb form of this term would be the two-word “set up”:

It took me hours to set up my computer.

Other terms where these rules apply include “workout” (verb = “work out”), “backup” (verb = “back up”) and “handout” (verb = “hand out”).

Look out for similar noun–verb distinctions in your writing!

Incorrect Compounds

Finally, some terms are incorrectly written as compound words even when there’s no correct version. Examples include “alot” (which should be “a lot”) and “nevermind” (which should be “never mind,” except the Nirvana album).

But these are simply errors and should be avoided in your written work.

In other cases, it is less clear. The word “alright,” for instance, is sometimes accepted as an alternative to saying “all right.” But “alright” is very informal. Some even consider it a spelling mistake. As such, you should be careful about using this compound word in formal writing.

And if you’re ever unsure about compounds, ask a proofreader for help!