Compound Words | Types, List & Definition

A compound word (sometimes just called a compound) is a series of two or more words that collectively form a single word. There are three types of compound words, which differ in terms of how they are written:

• An open compound word is written with spaces between the words (e.g., “secondary school”).
• A hyphenated compound word is written with hyphens between the words (e.g., “sister-in-law”).
• A closed compound word is written with no spaces or punctuation (e.g., “cheesecake”).

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Open compound words

Open compound words are written with spaces between the individual words. For example, “compound word” itself is an open compound word.

Open compounds are normally fairly new terms or are used only in specialist contexts. Over time, as they become more widely used, they tend to become hyphenated or closed compounds. But this is not universal: some well-established compounds such as “secondary school” continue to be written with spaces.

Many open compound words function as nouns and are formed by combining a noun with another noun or with an adjective.

Phrasal verbs are also normally written as open compounds. A phrasal verb is a series of two or more words (often a verb and a preposition) that functions collectively as a verb.

Note that normally open compounds are instead written as hyphenated or closed compounds in certain contexts. A compound noun is often hyphenated or closed when it’s used attributively (functioning as an adjective before another noun) or as a verb, and a phrasal verb is hyphenated or closed when it’s used as a noun.

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Hyphenated compound words

Hyphenated compound words are written with hyphens connecting the words. For example, “well-being” is a hyphenated compound word.

Hyphenated compounds are typically noun phrases being used as adjectives (e.g. “long-term”) or as verbs (e.g., “strong-arm”) or verb phrases being used as nouns (e.g., “check-in”) or as adjectives (e.g., “mind-blowing”).

Compound nouns were quite commonly hyphenated in the past but mostly aren’t now (e.g., “walking-stick” and “living-room” are now usually written “walking stick” and “living room”). But some remain hyphenated, especially if they consist of three or more words (e.g., “father-in-law”).

Closed compound words

Closed compound words are written without hyphens or spaces. For example, “babysitter” is a closed compound word.

Closed compounds can play a wide variety of roles, functioning as nouns (e.g., “weekend”), pronouns (e.g., “herself”), prepositions (e.g., “into”), adverbs (e.g., “however”), adjectives (e.g., “barefoot”), conjunctions (e.g., “whereas”), or verbs (e.g., “snowball”).

Closed compounds tend to be well-established words. They often start out as open compounds but close over time as they become more familiar. For example, compound indefinite pronouns used to be written as open compounds (e.g., “every one”, “some thing”), but now all except “no one” are closed.

List of compound words

The table below provides a representative selection of compound words, categorised by whether they are open, hyphenated, or closed and by what part of speech they function as.

You can observe some patterns in the table. For instance, there are many compound nouns; compound adjectives tend to be hyphenated; and some parts of speech only form compounds in certain ways.

Note that some words appear as more than one part of speech but may be written differently depending on their function. There may also be multiple ways of writing a single compound (e.g., “login” or “log-in”). Consult a dictionary if you’re unsure.

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Pluralising compound nouns

When you want to pluralise a noun that consists of multiple words, it can be difficult to know which word to pluralise. In a closed compound, it’s easy: the pluralisation always comes at the end, since it’s written as one word (e.g., “backpacks”, “houseboats”, “payouts”).

In open and hyphenated compounds, it varies; the final word is sometimes pluralised (e.g., “secondary schools”, “know-it-alls”), but sometimes an earlier word is instead (e.g., “attorneys general”, “men-of-war”). Usually, only one word is pluralised (e.g., “men-of-wars” is wrong).

To understand which word should be pluralised, look at the compound logically and consider which word “heads” the group – in other words, which one represents the thing being named?

• Frenches fry [Frenches that are fry?]
• French fries [Fries that are French]

• sister-in-laws [a sister (in multiple laws)?]
• sisters-in-law [multiple sisters (in law)]

But, admittedly, it can be hard to apply this logic in some cases (e.g., “merry-go-rounds”). If in doubt about how to pluralise a term, check a dictionary, where the correct plural noun will be listed in the entry.

Compound words vs other types of words

Compound words are one way of combining multiple words into one unit, but there are other ways too. Read on to see how compound words differ from:

• Portmanteaus
• Contractions
• Acronyms
• Simple and complex words

Portmanteaus

A portmanteau (also called a blend) is a word created by blending two words together. A portmanteau is different from a closed compound word because at least one of the words making it up is not used in its complete form: some letters have been removed or moved around.

For example, the portmanteau “chortle” is a combination of “chuckle” and “snort”. A part of the word “snort” has been inserted in the middle of the word “chuckle”, but neither word appears in full. As a closed compound, it might be “chucklesnort” or “snortchuckle” (not real words).

Contractions

Contractions are shortenings of existing words where the omitted letters are usually (not always) marked by an apostrophe. Sometimes, a contraction is a single word with some letters omitted (e.g., “talkin'”), but most commonly, it’s two or more words combined (e.g., “don’t”, “it’s”, “wanna”).

Combining contractions like this differ from compound words, again, because they don’t include the full words they are formed from: some letters are replaced with apostrophes and not pronounced.

Another difference is that contractions, especially less common ones like “wouldn’t’ve”, are generally avoided in formal contexts like academic writing, whereas there’s no problem with using compound words in such contexts.

Acronyms

An acronym is another way of shortening a series of words into one unit, in this case by reducing each word to its first letter (e.g., “NATO”: “North Atlantic Treaty Organization”) or occasionally its first syllable (e.g., “Benelux”: “Belgium, Netherlands, Luxembourg”).

Some acronyms are pronounced as full words (e.g. “NATO” is [nay-toe]), while others, often called initialisms, are pronounced as individual letters (e.g., “BBC” is [bee-bee-see]).

Again, they differ from compound words because they don’t include the full words that are being combined. Acronyms are fine to use in academic writing, as long as you define them on first use.

Simple and complex words

Simple words are words that cannot be broken down into smaller meaningful pieces. For example, “run” is a simple word – you could break it down into “ru” and “n”, but it’s clear that these don’t have any meaning on their own.

Complex words are composed of parts that each contribute some meaning to the whole. For example, “runner” consists of “run” (the verb it’s derived from, describing the action in question) and “-er” (a suffix used to indicate a person who does the action).

These individual units of sense are called morphemes: a simple word consists of just one morpheme, while a complex word consists of a main morpheme (called the root; “run” in our example) plus at least one other morpheme.

A compound word differs from a complex word because it’s made up of complete words that could also stand alone. In “runner”, it’s clear that while “run” is a word in its own right, “-er” is not. In contrast, the compound “runner-up” consists of two independent words, “runner” and “up”.

Worksheet: Compound words

Want to test your understanding of compound words? Check out the worksheet below. Try to find and highlight all the compound words in each sentence.

Other interesting articles

If you want to know more about nouns, pronouns, verbs, and other parts of speech, make sure to check out some of our other language articles with explanations and examples.

Frequently asked questions about compound words

Is “because” a compound word?

Yes, the conjunction because is a compound word, but one with a long history. It originates in Middle English from the preposition “bi” (“by”) and the noun “cause”. Over time, the open compound “bi cause” became the closed compound “because”, which we use today.

Though it’s spelled this way now, the verb “be” is not one of the words that makes up “because”.

Is “today” a compound word?

Yes, today is a compound word, but a very old one. It wasn’t originally formed from the preposition “to” and the noun “day”; rather, it originates from their Old English equivalents, “tō” and “dæġe”.

In the past, it was sometimes written as a hyphenated compound: “to-day”. But the hyphen is no longer included; it’s always “today” now (“to day” is also wrong).