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How to Craft Compound Nouns and Say Exactly What You Mean

There are a few universal English-related experiences we can all relate to: The joy of crafting the perfect sentence after 50 failed attempts. The exhaustion from doing a paper last-minute. The freeing feeling of adding the last citation to your bibliography. The agony of realizing you’ve been mispronouncing a word for years.

That last one may not be universal, but perhaps this one is: the suspicion that parts of the English language were created on a whim. Why else would we have words that change their meaning when they add a hyphen or remove a space? What is a compound noun if not utter madness?

While madness is not in the official compound noun definition, there’s no denying that learning how to form them can be frustrating.

We’ve created this guide to give you quick access to all the rules we believe you need to know, so you can take the guesswork out of it. Our smart proofreader can also help—it goes beyond offering just grammar and spell check, helping you to also detect passages that could be considered unintentional plagiarism.

What is a Compound Noun?

Compound nouns are created by joining two or more words together to form a new word or nominal phrase. Joining words to create new meaning occurs in other parts of speech as well. If you’re looking for an overview of how to combine words to create new meaning in other parts of speech, you can see it here.

To define a compound noun, you need to first look at its parts. The head of the word or phrase tells you what kind of thing the whole is referring to. The other words in the combination modify this head, or primary, word.

Let’s look at the example wildlife.

The word wildlife is made up of the words wild and life. Looking at each part, you can determine that the whole word is referring to life. Life, therefore, is the primary word, while the adjective wild is the modifier. Combined, they create a new word for undomesticated forms of life.

Wildlife is an example of a word in the closed form. These words can also appear in hyphenated form or open form (as two separate words). Some words even use more than one form, depending on the context.

Your style guide may also designate different punctuation or spelling for certain instances. MLA format, for example, uses an en dash when combining a multi-word phrase temporarily with mid, such as mid–twentiethcentury. Consulting with our library of resources and using our easy grammar checker will help you with formatting.

Closed Form Compound Noun List

What is a closed compound noun? Seen above in the word wildlife, this form contains neither spaces nor hyphens when combined. This form is frequently the result of a compound noun joining our lexicon through continued use. A phrase used in open form will transition to include a hyphen and, eventually, drop the hyphen and take on a closed form.

Not all compound nouns follow this pattern; the closed form works best with shorter words. The fewer syllables in a phrase, the more likely it is to become closed. English, of course, always has exceptions.

For example, the open dining room has kept “diningroom” out of our dictionaries. However, policeman and policewoman, words with the same or more syllables, have found their home there. Police officer, on the other hand, will likely remain open: the eo in a closed “policeofficer” might lead to pronunciation challenges.

Some closed words also have open or hyphenated forms. Pronunciation can help to determine whether the spelling should be open or closed in a given context. In closed form, the first syllable is typically stressed.

Consider this example: Greenhouse stresses green.

This closed form refers to a structure that houses plants. The open green house puts the stress on house and refers to a house that is green. Try saying them both in a sentence:

  • There’s a greenhouse next to that green house.

Below are some common closed form examples.

blackbird sunrise notebook
bystander afternoon toothpaste
website football bedroom

It’s easy to see how these words can confuse students and professors alike. Dining room, you’ll recall, remains open, yet bedroom and bathroom use the closed form. If you’re ever unsure about the form to use, check a recent dictionary for guidance. If there is no listing for the closed form, you can assume that the open form is appropriate.

Hyphenated Compound Nouns

Hyphenated compound nouns serve the same purpose as their open and closed siblings, but employ punctuation to join their parts and provide clarity.

A hyphenated compound noun’s definition is determined in the same manner as with open and closed forms. This process also serves to identify the word to pluralize when you need to increase the number of the word. Once you’ve identified the primary or head word, you apply the appropriate rule for increasing number to this part of the whole.

Let’s look at the word brother-in-law to illustrate this.

The primary word in brother-in-law is brother, which you determine by considering the meaning of the whole: a person who is a brother by law. Law, then, is modifying brother. To indicate more than one brother-in-law, you increase the number on the primary word brother, resulting in brothers-in-law.

The hyphen, as mentioned earlier, will sometimes, but not always, fall out of use as a word becomes established in the lexicon. A hyphen is frequently necessary to add clarity, as in this sentence:

  • The small horse breeder went to town.

Without a hyphen, it’s unclear whether a breeder of small horses went to town, or if the breeder of horses is himself small in stature.

Adding a hyphen to create a compound noun removes the ambiguity:

  • The small-horse breeder went to town.

American English tends to drop hyphens with some regularity and speed once a word comes into frequent use. As always, British English plays by the Queen’s rules, and words may maintain their hyphens indefinitely.

Due to these variances in usage and the potential for multiple forms, most style guides suggest consulting a dictionary for help with these words. Style guides do offer guidelines for some specific scenarios, however, such as how to add hyphens when two or more words act to modify the same term.

If you are formatting a paper, or creating a bibliography, our library of resources and citation generator can help you with APA format and more styles.

Examples of Separated Compound Nouns

When you create a word with a new meaning without merging its parts or using a hyphen, it is referred to as open. Not all words used to modify each other are compound nouns, however. To be defined as a compound noun, the two (or more) words must name a person, place, thing, or idea and create a new meaning when combined, rather than merely adding details. Below are some examples:

bus stop full moon swimming pool
ice cream water bottle dining room
mobile phone small talk washing machine

We use adjectives in English to modify words frequently, so it can be hard, at times, to determine if two words used together are a compound noun. To resolve this, consider whether the accompanying word is adding meaningor if their combination creates new meaning. Consider the following sentences:

  • Mary is waiting in the green room.
  • Mary is waiting in a green room.

In the first sentence, green room is a standard show business phrase for a waiting room or lounge. The two parts create a new word with a different meaning in this context. In the second sentence, green modifies room, but each word maintains its individual meaning.

At the risk of sounding like a broken record (two words that combine to create new meaning, you’ll note), the best course of action when unsure of the correct form is to consult a current dictionary.