A compound word is composed of two or more words that when combined have a different single meaning.

For example, gold and fish are words with different meanings. When combined as goldfish, they form a completely new word that includes the meanings of the two original words.

In this example, the first word (gold) modifies and describes the second word which identifies the original object (fish).

In the example below, the compound word is made up of two nouns. The first word (tooth) modifies and describes the second word (brush), telling us what its purpose is. 

➡ tooth + brush = toothbrush

There are three forms of compound words:

1. In the closed form, the words are melded together forming one single word. e.g: footprint, keyboard, makeup, crosswalk, skateboard.

2. In the hyphenated form, words are connected by a hyphen. e.g: mother-in-law, over-the-counter, six-pack, well-being.

3. In the open form, the words remain separate, but function together as a modified noun. e.g: high school, peanut butter, full moon, half sister, ice cream, middle class.

Unfortunately, there is no hard and fast rule on what form a compound word takes. However, there are a few general rules to guide spelling:

✅ Part of speech: Many compound words use different spelling when used as a noun, than when used as a verb or an adjective.

E.g: Back up

noun: The police officer called for backup.

verb: I back up my computer files everyday.

adjective: Do you have a backup plan in case it rains?

✅ Ambiguity: When in doubt, hyphenate. If the compound word will cause confusion in the sentence, use a hyphen to clarify that the words belong together.

E.g: He is a small-town doctor.

NOT He is a small town doctor.

Here, the hyphen clarifies that he is a doctor in a small town, rather than a small man.

✅ -LY: Words that end in -ly are never hyphenated when used in a compound word.

E.g: The ballet dancer is technically skilled.

Common compound words:

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Write in the comments section sentences using compound words.

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