Table of Contents
Introduction
Forming the plural of compound nouns might be confusing. Before exploring some quick tips to form these compounds, let’s review what compound nouns are first.
What Is A Compound Noun?
A compound noun is a noun made up of two or more words (e.g. toothpaste, haircut, or daughter-in-law). Most compound nouns can be formed as follows:
| Forms | Examples |
|---|---|
| noun + noun | train station |
| noun + adjective | handful |
| adjective + noun | blackberry full moon |
| verb (ing) + noun | breakwater swimming pool |
| noun + verb (ing) | haircut skydiving |
| verb + preposition | check-in |
| noun + preposition | passer-by |
| preposition + noun | underground |
| noun + preposition + noun | father-in-law |
The Plural Of Compound Nouns
As you can see from the examples above, some compound nouns are spelled as one word (e.g. handful), but others with hyphens (e.g. father-in-law) or separated by a space (e.g. full moon). Knowing how they are formed may help us understand how to form their plurals.
How To Form The Plural Of Compound Nouns
1. Typical Plural Form Of Compound Nouns
The plurals of compound nouns are generally formed by adding “s” to the principal word (i.e. the most significant word in the compound), also called the head of the compound. The head informs us about what the compound refers to. The other elements of the compound modify the head and are called the head ‘s dependents.
Examples:
| Compounds | Head | Plural |
|---|---|---|
| car park | park | car parks |
| blackboard | board | blackboards |
| mother-in-law | mother | mothers-in-law |
| taxi driver | driver | taxi drivers |
2. Compound Nouns With -Ful
Compound nouns with “-ful” (e.g. truckful, handful) may have two possible plurals. The “s” can be added either to
- The head noun (e.g. trucksful, handsful)
- Or to “-ful ” (e.g. truckfuls, handfuls).
It is just a question of consistency.
More examples:
| Compound nouns with “-ful” | Plural | |
|---|---|---|
| handful | handsful | handfuls |
| mouthful | mouthsful | mouthfuls |
| spoonful | spoonsful | spoonfuls |
| bucketful | bucketsful | bucketfuls |
| cupful | cupsful | cupfuls |
| truckful | trucksful | truckfuls |
3. Compound Nouns Ending In A Preposition
When the compound is formed with a noun and a preposition, (e.g. passer-by), the plural is formed by adding an “s” to the noun.
Examples:
| Compound Noun | Plural |
|---|---|
| passer-by | passers-by |
| hanger-on | hangers-on |
When neither compound element is a noun, the plural is formed by adding “s” to the last word. For example, the compound noun “grown-up” is made of the word “grown”, which is the past participle of the verb “grow”, and the preposition “up”. The plural of “grown-up” is formed by adding “s” to “up” (i.e. “grown-ups).
More examples:
| Compound Noun | Plural |
|---|---|
| grown-up | grown-ups |
| go-between | go-betweens |
| check-in | check-ins |
| higher-up | higher-ups |
| also-ran | also-rans |
Summary
Here’s a summarized table of the rules for forming the plural of compound nouns:
| Rule | Examples | Plural Form |
|---|---|---|
| Typical Plural Form | car park, blackboard, mother-in-law | car parks, blackboards, mothers-in-law |
| Compound Nouns with “-ful” | handful, mouthful, truckful | handsful/handfuls, mouthsful/mouthfuls, trucksful/truckfuls or handfuls, mouthfuls, truckfuls |
| Compound Nouns Ending in a Preposition | passer-by, hanger-on | passers-by, hangers-on |
| Neither Compound Element is a Noun | grown-up, go-between, check-in | grown-ups, go-betweens, check-ins |
Conclusion
Here are the main takeaways:
- The plural of compound nouns is generally formed by adding “s” to the principal noun as in “car parks“.
- To form the plural of compound nouns ending in “-ful”, add “-s” either to the principal noun or to the “-ful” part of the compound.
- When the compound is formed with a noun and a preposition, (e.g. passer-by), the plural is formed by adding an “s” to the noun.
- When neither compound element is a noun, the plural is formed by adding “s” to the last word.
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