Compound Nouns

A noun made up of two or more words is a compound noun. Sometimes, we write a compound as one word:

baseball, freeway, keyboard,
volleyball, pathway, toothpaste,
anybody, classroom, treetop,
thumbtack, eyebrow, pigpen

Often, we write compounds as two words:

elementary school, post office, swimming pool,
junk yard, nail polish, gold mine,
computer disk, cassette tape, snow tire,
rabble rouser, house mouse

Others are hyphenated:

brother-in-law, hand-me-down, take-off,
mother-in-law, great-great-grandfather, ex-president,
box-office, merry-go-round, forget-me-nots

There is no pattern for determining whether to spell a compound as one word, two separate words, or one hyphenated word. We must use the dictionary.

Examples 1

Write the compound nouns from this list:

elephant
dictionary
sister-in-law
hippopotamus
basketball
naturalization
milestone

eyelash
horses
pumpkin
compact disk
celebration
attorney
responsibility

show-off
trash can
cell phone
great-aunt
president
great-uncle

Solutions

The compounds from the list above are eyelash, show-off, sister-in-law, trash can, cell phone, compact disk, great-aunt, basketball, vice president, great-uncle, and milestone.

Forming Plurals with Compounds

Notice that we make the main element plural in a compound:

commanders-in-chief
mothers-in-law
zookeepers
footmen

powers of attorney
justices of the peace
Princes of Whales
songbirds

Notice that we do not use an apostrophe to form a plural:

Many songbirds (not songbird's) visit my bird feeder.

Examples 2

Write the plural form of each compound.

1. sister of the bride
3. king of Spain
5. groomsman
7. stepson
9. vice president
11. post office
13. computer disk
15. paper clip
17. secretary of state
19. hand-me-down
21. bird feeder

2. brother-in-law
4. matron of honor
6. chief of staff
8. officer of the law
10. nail polish
12. song of joy
14. wrist watch
16. shoe store
18. queen of England
20. great-grandfather

Solutions

We make the main element plural for each compound:

1. sisters of the bride
3. kings of Spain
5. groomsmen
7. stepsons
9. vice presidents
10. nail polishes
13. computer disks
15. paper clips
17. secretaries of state
19. hand-me-downs
21. bird feeders

2. brothers-in-law
4. matrons of honor
6. chiefs of staff
8. officers of the law
11. post offices
12. songs of joy
14. wrist watches
16. show stores
18. queens of England
20. great-grandfathers