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Compound nouns are nouns that are made up of two or more words that create a new noun with a unique meaning.

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• Compound Nouns in Use

  • Toothbrush (tooth + brush)
    – I have forgotten my toothbrush!
    
    
  • Sunflower (sun + flower)
    – A sunflower faces the sun as it moves through the sky.
    
    
  • Father-in-law (father + in + law)
    – My father-in-law will be visiting next week.
    
    
  • Airport (air + port)
    – The airport is closed due to the storm.
    
    
  • Parking tickets (parking + tickets)
    – After racking up parking tickets in three different towns, Dave decided it was time to start cycling.

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  * Compound Nouns

Forms of Compound Nouns

Compound nouns come in three forms.

• Closed form (no space between words): bedroom, haircut, firefighter, notebook, smartphone, blackboard, toothpaste, mailbox, keyboard, moonlight, hotdog
  
  
• Open form (space between words): post office, bus stop, full moon, coffee table, social media, bank account, credit card, living room, swimming pool, high school
  
  
• Hyphenated form (words joined with hyphens): mother-in-law, father-in-law, well-being, editor-in-chief, six-pack

An interesting thing about compound nouns is that their meaning often differs from the individual words that form them.

For example:

• I ate the best hotdog last night.

Compound noun example: Hotdog
Individual words: Hot (a high temperature) + dog (a canine animal).

Together these words form the word hotdog, which of course isn’t literally a hot canine but a type of food: a sausage in a roll.

The words hot + dog combine to create a new noun that is distinct in meaning from the original words.

Pluralising Compound Nouns

Compound nouns can be a bit tricky when it comes to pluralising them.

To make compound nouns plural, we apply standard noun pluralisation rules to the main word, and which word is the main word depends on the compound noun’s structure.

Note: Some compound nouns cannot be pluralised because they are uncountable, and thus always remain singular (e.g., real estate). For more details on countable and uncountable nouns, see our Countable Nouns & Uncountable Nouns page.

1) Closed Form

To pluralise a closed form compound noun, we treat it like any other noun. Apply the standard pluralisation rules to the end of the word. This might mean adding -s or -es, or using an irregular form (e.g., fireman > firemen).

Closed Form Compound Nouns: Singular vs. Plural

Singular	Plural
notebook	notebooks
bedroom	bedrooms
sunflower	sunflowers
firefighter	firefighters
toothbrush	toothbrushes
paintbrush	paintbrushes
butterfly	butterflies
fireman	firemen

2) Open Form

To pluralise an open form compound noun we add –s to the main word, which is usually the last word.

Open Form Compound Nouns: Singular vs. Plural

Singular	Main Word	Plural
parking ticket	ticket	parking tickets
dining table	table	dining tables
office chair	chair	office chairs
flower pot	pot	flower pots
book club	club	book clubs
ice cream	cream	ice creams
coffee shop	shop	coffee shops

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A small number of open form compound nouns are pluralised by changing the first word.

For example:

Singular	Main Word	Plural
attorney general	attorney	attorneys general
notary public	notary	notaries public
chief of staff	chief	chiefs of staff
court martial	court	courts martial
heir apparent	heir	heirs apparent

3) Hyphenated Form

To pluralise hyphenated compound nouns, we apply the standard pluralisation rules to the main word, whether that means adding -s / -es, or using an irregular form, just as with closed form compounds.

Pluralising hyphenated compound nouns can be challenging because it’s not always clear or intuitive which word is the main word.

Hyphenated Form Compound Nouns: Singular vs. Plural

Singular	Main Word	Plural
mother-in-law	mother	mothers-in-law
father-in-law	father	fathers-in-law
editor-in-chief	editor	editors-in-chief
commander-in-chief	commander	commanders-in-chief
governor-elect	governor	governors-elect
passer-by	passer	passers-by
six-pack	pack	six-packs
stand-in	in	stand-ins
hand-me-down	down	hand-me-downs
sit-up	up	sit-ups
warm-up	up	warm-ups
runner-up	runner	runners-up
church-goer	goer	church-goers
man-of-war	man	men-of-war

As shown in the table above, some hyphenated compound nouns pluralise by changes to the first word, while others require changes to the last word.

There are some recognisable patterns in how this type of compound noun pluralises. For example, compound nouns ending with in-law are always pluralised by changes to the first word:

• mother-in-law > mothers-in-law
• father-in-law > fathers-in-law
• brother-in-law > brothers-in-law
• sister-in-law > sisters-in-law

However, other hyphenated compound nouns, such as those ending in -up, don’t follow the same pattern.

• sit-up > sit-ups
• warm-up > warm-ups
• runner-up > runners-up

These inconsistencies can be confusing. Fortunately, there’s a simple framework we can use to identify which word to pluralise in hyphenated compound nouns.

Hyphenated Compound Nouns: Types & Pluralisation Rules

Hyphenated Compound Noun Type	Pluralisation Rule	Singular	Plural
Noun + Noun	Pluralise the main noun	mother-in-law	mothers-in-law
Noun + Preposition	Pluralise the noun	passer-by	passers-by
Number + Noun	Pluralise the noun	six-pack	six-packs
Verb + Preposition	Pluralise the last word	sit-up	sit-ups
Noun + Preposition	Pluralise the noun	runner-up	runners-up

Once we get familiar with these rules it makes dealing with the pluralisation of hyphenated compound nouns much easier.

[Noun] of [Noun] Phrases

Noun phrases that follow the pattern [noun] of [noun] (e.g., cup of tea) aren’t technically compound nouns, but they work in a similar way by naming a single, unified thing.

To pluralise these phrases, we typically pluralise the first noun (e.g., cups of tea).

The first noun usually changes while the second noun stays singular (e.g., buckets of water, not bucket of waters).

More examples:

[Noun] of [Noun] Phrases: Singular vs. Plural

Singular	Main Word	Plural
bucket of water	bucket	buckets of water
bottle of milk	bottle	bottles of milk
cup of tea	cup	cups of tea
work of art	work	works of art
bar of soap	bar	bars of soap
box of chocolates	box	boxes of chocolates
piece of cake	piece	pieces of cake

Practice Makes Perfect: Compound Nouns

Put your knowledge of compound nouns to the test here in our interactive practice section.

Exercise 1: Identify the Compound Noun

Identify the compound noun(s) in each sentence.

1. The firefighters rushed to the scene of the wildfire.
   
   
2. She bought a new bookshelf for her apartment.
   
   
3. The mother-in-law has offered to babysit the kids.
   
   
4. When it comes to negotiations, it’s always wise to sweeten the deal with an ice cream bribe.
   
   
5. The sunrise over the mountain range was stunning.
   
   
6. She much prefers part-time, especially with two young kids at home.
   
   
7. The breakthrough in research was unexpected.
   
   
8. He thought his hangover headache was bad. Then he saw his bank account balance.
   
   
9. They met at the coffee shop to discuss their project.
   
   
10. I’ve only ever bought second-hand. New cars depreciate too fast for my liking.
    
    
11. They gave out headphones to the passengers.
    
    
12. The class starts with a warm-up to get everyone moving.
    
    
13. Jenny spent the afternoon organising her bedroom wardrobe.
    
    
14. Social media can be both a blessing and a curse.
    
    
15. The local barber shop offers a discount on all haircuts for students.

Exercise 1: Answers [Click]

1. firefighters / wildfire
2. bookshelf
3. mother-in-law
4. ice cream
5. sunrise / mountain range
6. part-time
7. breakthrough
8. hangover / bank account
9. coffee shop
10. second-hand
11. headphones
12. warm-up
13. bedroom
14. social media
15. barber shop / haircuts

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Exercise 2: Pluralise the Compound Noun

Determine the plural form of each compound noun below.

1. passer-by
   
   
2. toothbrush
   
   
3. editor-in-chief
   
   
4. tomato plant
   
   
5. daughter-in-law
   
   
6. high school
   
   
7. sunflower
   
   
8. footstep
   
   
9. mother-to-be
   
   
10. warm-up

Exercise 2: Answers [Click]

1. passers-by
2. toothbrushes
3. editors-in-chief
4. tomato plants
5. daughters-in-law
6. high schools
7. sunflowers
8. footsteps
9. mothers-to-be
10. warm-ups

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Exercise 3: Choose the Correct Plural Form

Select the correct plural form for each compound noun.

1. Attorney General
   a) Attorney Generals
   b) Attorneys General
   c) Attorney’s General
   
   
2. Notary Public
   a) Notaries Public
   b) Notary Publics
   c) Notarys Public
   
   
3. Son-in-law
   a) Sons-in-law
   b) Son-in-laws
   c) Sons-in-laws
   
   
4. Coffee table
   a) Coffees tables
   b) Coffee tables
   c) Coffees table
   
   
5. Six-pack
   a) Six-packes
   b) Sixes-pack
   c) Six-packs

Exercise 3: Answers [Click]

1. b) Attorneys General
2. a) Notaries Public
3. a) Sons-in-law
4. b) Coffee tables
5. c) Six-packs

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Exercise 4: Fill in the Blanks

Complete each sentence with the correct plural form.

1. The __________ (runner-up) received medals for their efforts.
   
   
2. All the __________ (passer-by) stopped to watch the street performance.
   
   
3. She has two __________ (sister-in-law) who live abroad.
   
   
4. __________ (Secretary-General) from various international organisations will be meeting at the summit.
   
   
5. The newly built apartments offer bright __________ (living room) with large windows and open spaces.

Exercise 4: Answers [Click]

1. runners-up
2. passers-by
3. sisters-in-law
4. Secretaries-General
5. living rooms

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Exercise 5: Correct the Errors

Correct the compound noun errors in each sentence.

1. The keysboard are on offer here. You should buy one!
   
   
2. She felt a sense of peace at the sight of butterflys flitting around the garden.
   
   
3. The passers-bys didn’t notice the sign and one of them fell into the pond.
   
   
4. She has two brother-in-laws.
   
   
5. He bought a bigger dinings table in the hopes they’d have more family meals together.

Exercise 5: Answers [Click]

1. keyboards
2. butterflies
3. passers-by
4. brothers-in-law
5. dining table

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