Compound words are when two or more words combine to form a new single word or a phrase that acts like a single word. There are three different types of compound words in grammar: open compound words with spaces between the words (ice cream), closed compound words with no spaces (firefighter), and hyphenated compound words (up-to-date).
While compound words are a part of everyday communication, figuring out whether to use spaces, hyphens, or neither can get confusing. Below, we discuss the rules for compound words in grammar, including the three different types of compound words, and give examples.
What is a compound word?
Compound words are individual words (or phrases that act as individual words) made from two or more words working together. They can be most parts of speech, including nouns, verbs, adjectives, adverbs, and even prepositions like inside, outside, within, and without.
Compound words have their own distinct meanings that are different from the meanings of the words they’re made of. For example, the compound word grandparent is made from the individual words grand and parent. While grandparents are similar to parents, they’re not the same—and not all grandparents are grand, either!
Instead, the compound word grandparent acts as its own word with its own unique definition, distinct from the definitions of grand and parent. All compound words work like this, even open compound words without spaces. For example, the page in web page is not the same as the page in a book, nor does it involve webs.
Compound words are often confused with blended words, also known as portmanteaus, but the two are very different. In compound words, each individual word remains unchanged. However, in portmanteaus, or blended words, only parts of each word are used. For example, the word internet is a portmanteau; it’s a combination of the words interconnected and network. If it were a compound word, it would be something like interconnected-network, with both words remaining whole and uncut.
The 3 types of compound words
There are three types of compound words in grammar, determined by how the words are separated.
- Open compound words: spaces between the words
- Closed compound words: no spaces between the words
- Hyphenated compound words: hyphens between the words
The different categories of compound words pertain only to the words’ spellings—they don’t affect how the words are used or pronounced. Still, it’s important to understand their differences because you need to use the correct spelling when you’re writing. Let’s look at each group on its own and review a special compound words list for each.
1 Open compound words
Open compound words have spaces in between the words, which can make them hard to identify. But despite how they look, open compound words always act like single words. They always appear together, in the same order, and they each have their own unique meanings.
Open compound words are mostly nouns, and they’re used the same as regular nouns. If you want to make an open compound word plural, you usually pluralize only the final word in the group, not all the words.
Mia got sick from eating ten hots dogs.
Mia got sick from eating ten hot dogs.
When open compound words are verbs, they’re more commonly known as phrasal verbs. Phrasal verbs have their own special rules, but in general only one of the words in the group is conjugated while the others remain untouched.
He found outed too late.
He find outed too late.
He found out too late.
However, be careful because sometimes open compound words take a hyphen if they are used as a different part of speech. For example, the compound word test drive is open when used as a noun but hyphenated as test-drive when used as a verb.
Test drives are important. I always test-drive a new car before purchasing.
Examples of open compound words
- black eye
- cell phone
- close call
- common sense
- cotton candy
- dining room
- first aid
- full moon
- French fry
- heart attack
- high school
- hot dog
- ice cream
- life jacket
- living room
- no one
- peanut butter
- post office
- prime minister
- real estate
- remote control
- report card
- rib cage
- role model
- roller coaster
- salad dressing
- search engine
- slam dunk
- sleeping bag
- time capsule
- vacuum cleaner
- vending machine
- video game
- waiting room
- washing machine
- web page
2 Closed compound words
Compared to open compound words, closed compound words are much easier to remember and to use. There are no spaces between the words, so closed compound words both look and act like individual words.
You can find closed compound words in almost all parts of speech. Adverbs like sometimes or anyday are closed compound words, as are the prepositions inside, outside,within, and without. Even the word cannot, a shortened form of the phrase “can not,” is a closed compound word.
Examples of closed compound words
- airport
- anybody, everybody, nobody, somebody
- anyone, everyone, someone (but not no one), anything, everything, nothing, something
- anywhere, everywhere, nowhere, somewhere
- babysit
- background
- barefoot
- baseball, basketball, football, etc.
- bathroom
- bedroom
- blackberry, blueberry, etc.
- breakfast
- cannot
- checkout
- cowboy
- daylight
- desktop
- fingerprint
- firefly
- forever
- gentleman
- grandmother, grandfather, granddaughter, etc.
- grapefruit
- grasshopper
- headquarters
- handshake
- inside
- keyboard
- lipstick
- mailbox
- nevertheless
- nonetheless
- notebook
- outside
- payday
- railroad
- rainbow
- raincoat
- skateboard
- smartphone
- snowball
- sometimes
- sunflower
- toothbrush
- turntable
- undercover
- upstream
- waterfall
- watermelon
- weekend
- within
- without
3 Hyphenated compound words
Last are hyphenated compound words, which have hyphens between the words. These can be tricky to spell if you’re unsure whether there’s a hyphen or a space, so it’s best to familiarize yourself with a compound word list to help you learn the individual spellings. Otherwise you can quickly look up the correct spelling with a spell checker.
When hyphenated compound words are nouns, it’s important that you pluralize the right part. Unlike with open compound words, you don’t always pluralize the final word in the group. For example, with the hyphenated compound word mother-in-law, you pluralize mother instead of law.
Some spouses don’t like their mother-in-laws, but I get along with mine.
Some spouses don’t like their mothers-in-law, but I get along with mine.
However, each hyphenated compound word is different, and sometimes the s comes at the end. For example, the plural of merry-go-round is merry-go-rounds.
The merry-go-rounds are my favorite part of any amusem*nt park.
As an adjective, a hyphenated compound word acts the same as a hyphen with compound modifiers.
The twenty-year-old students tried a long-distance relationship.
Examples of hyphenated compound words
- check-in
- clean-cut
- editor-in-chief
- empty-handed
- far-fetched
- father-in-law, mother-in-law, sister-in-law,etc.
- free-for-all
- know-how
- know-it-all
- life-size
- merry-go-round
- long-distance
- long-term
- mind-blowing
- nitty-gritty
- one-sided
- one-dimensional, two-dimensional, etc.
- over-the-counter
- run-in
- runner-up
- strong-arm
- topsy-turvy
- toss-up
- up-to-date
- well-being
- word-of-mouth
Compound word FAQs
What are compound words?
Compound words occur when two or more words combine to form one individual word or a phrase that acts as one individual word. Common examples of compound words include ice cream, firefighter, and up-to-date.
How do compound words work?
In grammar compound words act as individual words. This means that when you’re conjugating compound verbs or pluralizing compound nouns, you only make the grammatical changes once. For example, if you want to talk about more than one living room, you say living rooms, not livings rooms.
What are the different types of compound words?
There are three types of compound words: open compound words, which have spaces between the words (dining room); closed compound words, which have no spaces (babysit); and hyphenated compound words, which have hyphens (free-for-all).
