The word compound means one thing that is composed of two or more elements. When you hear the word compound, you might think of a chemical compound, compound interest, or you might just use the word as a synonym for a mixture. Compounding is also a grammatical phenomenon, and there is a lengthy list of compound words in the English language.
Compound Words Definition
Simply put, compound means one thing made of many things. The definition for compound words means just that.
Compound words: two or more words joined to create a new meaning.
Compound words are not two random words thrust together. Compound words will be two words that are frequently found together, such as late-night, nice-looking, or seafood.
Compound words are usually two base words used together. Remember, base words are standalone words that signal a particular meaning, even when stripped of affixes (example: success in successful).
That’s not to say, however, that compound words can’t use derived words. Derived words are words that are built on a root, typically with the addition of an affix (example: teach + er = teacher). Many compound words include derived words (coffee maker, sewing machine, skyscraper).
The process of compounding is different from derivation and inflection — both of which typically involve adding an affix to change a word’s grammatical category. While derivation, inflection, and compounding are all a process for creating new words, compounding uses two base words, rather than a single base word and an affix (e.g., -ing, im-, or -ed).
Compounding in English Examples
Compounds help us understand words as a single unit, which in some cases helps to clarify the meaning of a word or phrase in English.
Let’s look for a vegan-friendly restaurant.
Fig. 1 - A "vegan-friendly" restaurant is different from a "vegan, friendly" restaurant.
Using a hyphen here shows the reader that the words vegan and friendly should be taken as a single unit. Otherwise, it might be read as, “Let’s look for a vegan friendly restaurant,” with vegan and friendly being two different adjectives to describe a restaurant.
When new things, ideas, or phrases come into the collective consciousness of the public, they need a name or something people can say to refer to them. Compounding words is one of the most (if not the most) common types of word formation in English because it is so easy to do.
These new words can be figurative like chairman (the head of a committee or group, not a chair-shaped man), or simply a combination of the meaning of each of the base words, like lighthouse (a house of light).
Just email me, and I’ll respond to it later.
The word email wasn’t used until the late twentieth century because email, or electronic mail, didn’t exist until then. There was a need to create a word to communicate this new idea of sending a message electronically, and e-mail —which became email, without the hyphen — was a simple option.
Types of Compound Words
There are three types of compound words: open, closed, and hyphenated.
Open Compounds
Open compound words are formed by combining an adjective with the noun it modifies to create a new noun. These compound words are usually the result of two words being so frequently used together that they eventually come to mean one specific thing.
Shopping cart
Potting soil
Real estate
Even though these words are separated with a space, they’re still considered a single unit. You can tell it’s an open compound word, rather than merely a noun modified by an adjective, because the two words are so regularly used together to mean something specific.
For example, real is not used as the modification of the word estate to express it’s real as opposed to a fake estate. Real estate is the business of buying and selling property and buildings on said property.
Closed Compounds
Closed compound words look the most like a “real word” because there is no space between the two roots.
Keyboard
Pothole
Tablecloth
Two words might form a closed compound because they are so frequently used together.
Fig. 2 - Email is a newer word that came from two base words: electronic and mail.
In the 1990s when someone wanted to connect to the internet, they might say they were going to go on-line (cue the sounds of dial-up internet and a male voice saying, “You’ve got mail”). Today in the twenty-first century, the internet is a part of our everyday experience, and so the word has lost its hyphen and is typically shortened to online.
Hyphenated Compounds
The final type of compound words are hyphenated compounds. These are words that — just like closed and open compounds — are frequently used together. The hyphen connects these words, so they function as one unit.
A hyphen (-) is a punctuation mark that shouldn’t be confused with a dash (–). A hyphen connects two words or word parts, whereas dashes indicate a pause or range. Dashes can be short (an “en dash” which is the length of the letter n) or long (an “em dash” which is the length of the letter m).
Long-term
Close-up
Empty-handed
Many hyphenated compounds become closed compounds if they’re used frequently enough.
Hyphenating Compound Words
You might wonder, “How do I know when to hyphenate a compound word?” There are many rules regarding hyphens in general, and here are the ones that are key in hyphenating compound words.
Only hyphenate when the compound comes before the noun it will modify. If it comes after, don’t include a hyphen.
The man-eating bear was only a few yards away. vs. The bear was definitely a man eater.
When a compound modifier contains an adverb ending in -ly and a participle or adjective, don’t use a hyphen.
Unfortunately, there is not always a consensus about whether to hyphenate compound words or create a closed compound word. If you’re ever in doubt about whether to hyphenate a compound word, consult a dictionary or the appropriate style guide for a definitive answer.
Compound Words List
Here is a longer compound words list for reference.
Open Compound Words
Sun room
Cheer up
Summer break
Garage sale
Dress up
Fire pit
Jumping jack
Science fiction
Vice President
Swimming pool
Closed Compound Words
Dishware
Bookstore
Seatbelt
Birthday
Carpool
Limelight
Comeback
Candlelit
Football
Lawsuit
Hyphenated Compound Words
House-of-mirrors
Self-contempt
Father-in-law
Well-read
Full-length
Free-fall
High-rise
Life-size
Deep-fried
Right-handed
Compounding - Key takeaways
- Compound words are two or more words joined to create a new meaning.
- Compound words are usually two base words used together.
- Compounds help us understand words as a single unit, which in some cases helps to clarify the meaning of a word or phrase.
- There are three types of compound words: open, closed, and hyphenated.
- There is not always a consensus about whether to hyphenate compound words or create a closed compound word.
Explanations 
Textbooks 
Exams 
Magazine 
