Compound Nouns: What They Are and Common Examples

When two or more words join together to make a single word, like keyboard or bookstore, that's a compound word. A compound noun is a type of compound word that is used to designate a person, place or thing. Keep reading to learn more about the different types of compound nouns and common examples of each.

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What Is a Compound Noun?

A compound noun is a compound word that functions as a noun. The first part typically states the type or purpose, and the second part states who or what is being named. For example, in the word firehouse, the word "fire" indicates what type of house it is (one for fighting fires). The meaning of the new word is different than either of its parts individually.

Examples of closed form (no space or hyphen) compound nouns in sentences include:

  • The lighthouse directs ships away from the rocks.

  • Watch the butterfly on the flower over there.

  • You should secure your furniture in case there's an earthquake.

Compound nouns can also be in hyphenated form. These include:

  • Janice works out so much that she has a six-pack.

  • Give the balloon to the five-year-old in line.

  • You're such a sweet son-in-law for giving me this card.

Finally, you'll also find compound nouns in open form with a space between the words. Some examples are:

  • Can we stop by the post office later today?

  • This tax cut is just for the middle class.

  • She is the first female attorney general of our state.

How to Form Compound Nouns

You can use any parts of speech to create a compound noun, not just nouns, as long as it functions as a noun in the sentence. The other parts of speech used to create compound nouns may be adjectives, prepositions or verbs.

Depending on the parts of speech used to create the compound noun, the rules for word form can vary as well. For example, the word redhead means "a person who has red-orange hair," but red head means "a head that is red." Take a look at these common combinations that make up compound nouns and general rules regarding the forms each combination typically takes.

Parts of Speech

Examples

Typically Closed, Hyphenated or Open?

noun + noun

toothpaste, wallpaper, fish tank

closed, but sometimes open (depending on the word)

adjective + noun

top hat, bluebird, redhead

closed, but sometimes open (depending on the word)

noun + adjective

spoonful, truckload, wireless

closed

preposition + noun

underworld, bystander, afterlife

closed

noun + preposition

hanger-on, passer-by

hyphenated

noun + prepositional phrase

ten-year-old, father-in-law, lady-in-waiting

hyphenated

verb + noun

chopstick, swimsuit, washing machine

closed, but sometimes open (depending on the word)

noun + verb

haircut, snowfall, photo shoot

closed, but sometimes open (depending on the word)

adjective + adjective

turquoise blue, golden yellow

open

adjective + verb

dry-cleaning, public speaking, wet sanding

hyphenated or open (depending on the word)

preposition + verb

output, backbone, overthrow

closed

verb + preposition

touchdown, check-in, drawback

closed or hyphenated (depending on the word)

Closed, Open or Hyphenated?

Truth be told, there are no rules governing why some compound words are hyphenated, some are closed and others remain open. Like irregular verbs, you simply have to study a word list or consult your dictionary.

In American English, common words are typically closed, and uncommon words often use hyphens or open forms. It's also worth noting that compound nouns that have become commonplace sometimes lose the space or hyphen over time. For example, “on-line” is now online. “Take-out” is now takeout. British/Canadian English typically uses a hyphen. For example, the Shorter Oxford Dictionary uses pot-belly while the American Heritage Dictionary uses potbelly.

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Hyphenating Compound Nouns with Verbs

The trickiest category for people tends to be the ones with verbs. Some words are more obvious than others (swimming pool, public speaking), but others seem trickier (decision-making or decision making?). The decision to hyphenate or not depends on the style guide you're using, and usually it depends on the particular word. It also depends on whether you're using the word as a compound noun or as a compound adjective, which has its own set of rules.

Plural and Possessive Rules for Compound Nouns

How do you make these compound nouns plural or possessive? To no surprise, there are no hard and fast rules concerning the plural form of compound words, especially since some hyphens are omitted over time.

Some of the more common rules include:

  • In hyphenated words, usually the "s" goes at the end of the noun, as in daughters-in-law or mayors-elect.

  • Sometimes the “s” is at the end, as in go-betweens and higher-ups.

  • In the open form, the "s" is often added to the noun, as in bills of fare, secretaries of state, notaries public, and full moons.

To make a compound word possessive, you usually add apostrophe + s to the end of the word, as in mother-in-law's car or five-year-old's birthday.

If the compound word is plural, it can get a little strange with two "s" sounds close together, as in fathers-in-law's attire. If you can, it would be better to reword the sentence so the plural compound word does not need to be possessive: the attire of the fathers-in-law.

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Compound Noun vs. Noun Phrase

Compound nouns are slightly different than noun phrases, which are modifier + noun phrases. For example, a hot dog is a type of sausage typically eaten on a bun. It may be hot, but it's certainly not a dog.

The combination of these two words means something entirely different than the mere combination of the adjective "hot" and the noun "dog," which would refer to an overheated canine. Observe the difference below:

  • I want to eat a hot dog when we go to the county fair.

  • The hot dog was grateful to find a shady spot for a nap.

The first sentence uses "hot dog" as a compound noun, but the second does not. You can usually tell the difference by carefully reading the sentence context, and by listening to the pronunciation. Compound nouns typically have a stress on the first word ("HOT dog" — the food) while noun phrases have no stress on either word ("hot dog" — a dog that is hot.)

Making Language Richer

Compound nouns are just one way in which the English language has become richer over time. While your brain is wrapping itself around the subject, take a look at the cousins to compound nouns. Taking the time to familiarize yourself with compound adjectives and compound verbs will help you round out your understanding of compound words.