Compound Words: What Are Compound Words? Definition and Examples

By Carly Forsaith, updated on May 31, 2023

Do you keep hearing about compound words but aren't sure what they are? In that case, you've come to the right place, as that's precisely what this article will address. You'll learn everything you need to know about compound words in order to use them correctly.

In short:

  • Compound words consist of two or more words joined together to form a new word. There are three types of compound words: open, closed, and hyphenated.

This guide is part of our free online Grammar Book.

What Are Compound Words?

The first place to start is with the question, "What are compound words?"

  • When two or more words come together to form a single word, that's a compound word.
  • The compound word has a new and distinct meaning created by the two terms it's made up of.

Compound words can be almost any part of speech, but most commonly, you'll find:

Here's an example of each:

Vampires only come out in the nighttime.

I'm looking for a part-time job.

We hope this loan will help kick start your business.

Not all compound words are made up of two words, mind you. You can also form a compound word by combining a word element with a word.

The three-word elements in English are:

  • prefixes (anti-, im-, non-, pre-)
  • suffixes (-ful, -ment, -ion, -dom)
  • combining forms (mini-, macro-, psuedo-, -graphy, -logy)

Here are some sentences with these types of compound words:

It always seems impossible until it's done.

The lion rules the animal kindgom.

We're putting together a choreography for the school show. 

When you blend two words together to make a compound word, you keep both words in their entirety. This is unlike a portmanteau, where at least one of the words is cropped.

Some examples include:

  • 'Glamping,' a mixture of 'glamour' and 'camping.'
  • 'Brexit,' a mixture of 'Britain' and 'exit.'

As for the meaning, that's where things get a little complicated. Sometimes, the two words together form an entirely new meaning that has nothing to do with the individual meaning of each word. For example, when a plane 'takes off,' this has nothing to do with taking or being 'off.' Other times, the meaning is a mixture of the two words' meanings.

For example:

  • A 'boyfriend' is a 'friend' who's a 'boy.'

It's worth noting that although we say that compound words are made up of two or more words, most compound words combine just two words. But it definitely isn't impossible to find compound words made up of more than two words. Usually, though, these words aren't as frequently used.

For example:

  • whatsoever
  • longshoreman
  • aircraftman
  • workmanlike
  • hereinafter

Now that we've covered the meaning of a compound word, let's look at the different types of compound words.

Types of Compound Words

There are three types of compound words:

  • Open compounds
  • Closed compounds
  • Hyphenated compounds

Let's take a deeper dive into each type, one by one.

Open Compounds

Open compounds are made up of two words with a space between them. They're tricky to differentiate as compound words because they just look like two separate words. So mostly, we rely on our common sense. Take the word 'hot dog'; this is an example of an open compound word. When you see these two words in a sentence, you know that they are to be read and understood as a unit and not as 'hot' and 'dog.'

The word high school is another example.

  • When you see these two words together, you know the writer isn't referring to a school that is high up on a hill.
  • It's clear the two words are to be interpreted as a unit to refer to a secondary school.

Watch out, though! Sometimes an open compound can become a hyphenated compound if used as a different part of speech. For example, the noun video game is an open compound word, but if you use it as a modifier, it becomes a hyphenated compound.

Let me illustrate:

He loves to play video games.

He is an avid video-game collector.

Most open compound words will be nouns, adjectives, or verbs. But you will also come across different types, such as prepositions ('in front of') and adverbs ('early on').

Open Compound Nouns

Most open compounds are nouns and can comprise a modifier + a noun. This holds up for our two previous examples. 'Hot' is an adjective, and 'dog' is a noun,' and together they make the noun 'hot dog,' which is a popular food. 'High' is an adjective, and 'school' is a noun, and together they form the noun 'high school,' a type of educational institution.

Sometimes they're formed with a verb + a noun, like in the word 'heart attack.' Though the word 'heart attack' contains two different parts of speech, a verb, and a noun, together they make a noun.

You can also form an open compound noun with two nouns, like with the word 'car park,' made up of the noun 'car' and the noun 'park.'

Here are some example sentences that contain open compound nouns:

Can I have a bagel with cream cheese and salmon, please?

He's old enough to start catching the school bus in the mornings.

Let's meet at the swimming pool at 2pm. 

Note that if you want to pluralize an open compound noun, you'll need to pluralize the final word of the phrase. You'll say 'school buses' and not 'schools bus.'

Open Compound Adjectives

You can also find open compound adjectives. You can make them using adverb + past participle, verb + adjective, and several other combinations.

Here are some examples of open compound adjectives in sentences:

She was wearing an emerald green dress.

I'm now offering pro bono services for families on a low income.

He has a very tightly wound wife.

Open Compound Verbs

Open compound verbs are also more commonly known as phrasal verbs. They're usually made up of a verb + another word. That other word is often a preposition.

He can't join us on the trip because he's just come down with a cold.

I can't believe your car broke down again!

The plane's ready for take off.

Note that to conjugate phrasal verbs into the various tenses, you should conjugate the actual verb part of the phrase, not the preposition. You would say 'broke down' and not 'break downed.'

Closed Compounds

Moving onto closed compounds now, which are two words joined together to form a single word. There is no space between them.

Closed compounds come in almost any part of speech:

  • nouns ('airport')
  • pronouns ('everyone')
  • prepositions ('within')
  • adverbs ('nevertheless')
  • adjectives ('makeup')
  • conjunctions ('whereas')
  • or verbs ('cannot')

You can make them using several combinations, like:

  • noun + noun,
  • preposition + preposition,
  • verb + preposition, and so on.

Here are some example sentences that use closed compounds:

We can't wait to meet your new boyfriend.

My son's babysitting while we go out to celebrate our anniversary.

I'm so used to my morning coffee, I don't think I could do without.

Closed compounds are easier to handle than open compounds because they are used just like a single word. So, for instance, when pluralizing an open compound, you have a choice between two words, but with a closed compound, you just pluralize the only word there is 'boyfriend' becomes 'boyfriends.'

The same applies when conjugating a closed compound verb. 'Babysitting' in the past tense becomes 'babysat.'

Hyphenated Compounds

The third and final type of compound word is the hyphenated compound. As you might have guessed, it features two words joined together by a hyphen.

Hyphenated compounds can be:

  • adjectives ('over-the-counter')
  • verbs ('co-sign')
  • adverbs ('self-consciously')
  • or nouns ('tongue-twister')

Various combinations are available for making hyphenated compounds, from:

Here are some sentence examples that use hyphenated compounds:

Would you like me to gift-wrap that for you?

She's a cold-blooded murderer.

I've been promoted to editor-in-chief!

Hyphenation Rules

You can memorize some general rules to ensure you're hyphenating your compound words correctly. But the thing about compound words is that they can very much fluctuate between the three different types. As well as this, they often change over time as they become more and more common.

As Merriam-Webster explains:

Historically, a lot of compounds follow the pattern of entering English as open compounds, then gradually take on hyphenation and eventually a closed form as they become more familiar. 

Let's take as an example one of the main rules: a compound word should be hyphenated if it precedes the noun it modifies and open if it follows it.

Case in point:

That's a strange-looking insect.

That insect is very strange looking. 

There are exceptions to this rule. For example, the words 'health care' and 'real estate' are never hyphenated, even if they come before the noun they modify.

Then you've got words that can be hyphenated, open or closed, like 'lifestyle'/'life style'/'life-style'. Not to mention a lack of clarity around words more recently added to the English language, like words about the internet and computing. 'Email' vs 'e-mail' and 'website' vs 'web site.'

You might feel that this is all very confusing, but it's actually good news. It means that there aren't hard-and-fast rules you have to stick to and that you have a certain amount of creative freedom. The main thing you want to look out for is to ensure your intended meaning is clear. After all, that's the whole point of hyphens to show that words are connected. Therefore, if you feel it's obvious enough that two words are connected, you can often omit the hyphen. If you're unsure, use a hyphen. You won't be penalized for it.

Here's an example where the hyphen helps provide clarity:

Lisa is a hungry-caterpillar feeder.

Lisa is a hungry caterpillar feeder.

In the first example, the adjective 'hungry' is connected to the noun 'caterpillar,' showing that Lisa is a person who feeds hungry caterpillars. In the second, the lack of a hyphen makes it unclear to whom the adjective 'hungry' relates to, meaning it could be interpreted that Lisa is a hungry person who feeds caterpillars.

Suspended Compounds

Using suspended compounds is a way of avoiding repetition when it comes to writing a set of compound words that have an element in common.

Here's an example:

I'm applying to part- and full-time jobs.

The compound words 'part-time' and 'full-time' have the noun 'time' in common, so it's unnecessary to repeat them. You need only write it once (on the last word), as long as you use a hyphen followed by a space on all the other words. It also works with sets of more than two compound words:

The party was mostly attended by three-, four- and five-year-olds.

Pluralizing Hyphenated Compounds

What about if you need to pluralize hyphenated compound nouns? We discussed how to do that for open and closed compounds, so let's find out how to do it with hyphenated ones.

  • Note that this only applies to nouns since other parts of speech can't be pluralized.

The rule goes that if a compound word is hyphenated, you should pluralize the principal word. Which of the words is the principal word is down to you to decide. Most of the time, this will simply require a little common sense.

Take the word 'sister-in-law,' for example. It's clear that the principal word is 'sister' because the terms 'in' and 'law' are just there to modify it. So if you wanted to pluralize this hyphenated compound word, you'd pluralize 'sister,' and you'd end up with 'sisters-in-law.'

Let's try that with some more examples:

  • passer-by → passers-by
  • jack-of-all-trades → jacks-of-all-trades
  • changing room → changing rooms

The exception to this rule is with hyphenated compound words made of a verb and a preposition. Then, you'd always pluralize the last word, regardless of what the principal word is.

  • sign-off → sign-offs
  • take-out → take-outs
  • build-up → build-ups

Another exception is when there is no principal word because none of the original words' meanings relate to the new word they've come together to create. Take the word 'forget-me-not,' for example, which is a type of flower. The words 'forget,' 'me,' and 'not' are irrelevant here; the only word that counts is the new word they make together. In this case, pluralize the last word. In this case, 'forget-me-nots.'

Conjugating Hyphenated Compounds

Hyphenated compound verbs act just like regular verbs, which means they can be conjugated into different tenses. We already learned how to conjugate open and closed compound verbs, but what about hyphenated compound verbs? Easy peasy! Just conjugate the verb element of the compound, and leave the rest as is.

  • sun-dry → sun-dried (past indefinite)
  • ice-skate → ice-skating (present participle)
  • fist-pump → fist-pumped (past participle)

Concluding Thoughts on Compound Words

That concludes this article on compound words. I hope you found it helpful and that you now feel confident using them in your own writing.

Let's summarize what we've learned:

  • Compound words are made up of two or more words merged to create a new word.
  • There are open, closed, and hyphenated compound words.
  • Compound words can take on the role of almost any part of speech.
  • To create a compound word, you can use a combination of different parts of speech. 
  • You can pluralize and conjugate compound nouns and verbs. 
  • Rules around which category of compound certain words should fall into are pretty flexible, and opinions vary.

If you enjoyed this article, check out our Grammar Book, a free online database full of articles breaking down complex grammar concepts, just like this one.

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Written By:
Carly Forsaith
Carly Forsaith is one of the lead freelance writers for Carly is a copywriter who has been writing about the English language for over 3 years. Before that, she was a teacher in Thailand, helping people learn English as a second language. She is a total grammar nerd and spends her time spotting language errors on signs and on the internet.

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