Definition: A compound noun is a noun made up of two or more words. Each word makes up part of the meaning of the noun.
Compound nouns can be written three ways:
A single word
A compound noun is the sum of its two parts. However, there are some words that aren't compound nouns even though they can be broken up into two words. One example is a compound adjective.
A half-eaten pie
(Half-eaten describes the pie, so it is an adjective, not a noun.)
Two-word proper nouns can also be classified as compound nouns. Remember that proper nouns name specific people, places, and things.
Single-word compounds and hyphenated compounds are easy to spot, but two-word compounds can be tricky. Ask yourself, "Would I find both words together as a single entry in the dictionary?" For example, if you compare the phrase cold water with the compound noun ice cream, you can see the difference. In the phrase cold water, cold is an adjective that describes the noun water. However, ice cream is a compound noun because ice is not an adjective describing cream. The two words work together to create a single noun. To check the spelling of a compound noun, look it up in the dictionary.
When a compound noun is a single word, make it plural by adding s to the end. If the compound noun is hyphenated or composed of two separate words, remember to add s only to the word that is plural.
one mother-in-law ⇒ two mothers-in-law
(There are two mothers, not two laws.)
one director general ⇒ two directors general
(There are two directors, not two generals.)
Practice What You've Learned
Click on the compound nouns in each sentence. If the compound noun is written as two words, be sure to click on both parts.