Forming Plurals of Compound Nouns
Pluralizing the Different Types of Compound NounThis infographic summarizes how to pluralize a compound noun:
(Rule 1) Forming the Plurals of Hyphenated Compound NounsWhen a compound noun is hyphenated, add "s" to the principal word. (In these examples, the principal words are in bold.)
(Rule 2) Forming the Plurals of Multi-Word Compound NounsWhen a compound noun consists of two or more words, add "s" to the principal word. (In these examples, the principal words are in bold.)
|Knight Templar||Knights Templar|
|bus stop||bus stops|
|full moon||full moons|
(Rule 3) Forming the Plurals of Compound Nouns without a Principal NounIf there is no principal word, follow the usual rules for forming a plural, which usually means adding "s" to the end of the word.
(Rule 4) Forming the Plurals of Single-Word Compound NounsWhen the compound noun is a single word, follow the usual rules for forming a plural (i.e., pluralize the ending).
(Rule 5) Forming the Plurals of Terms in the Form [Word] "of" [Word]With a term in the form [word] of [word] (e.g., "cup of tea"), the first word is always the principal word. Form the plural by pluralizing the first word.
|cup of tea||cups of tea|
|man of war||men of war|
|right of passage||rights of passage|
(Rule 6) Forming the Plurals of Compound Nouns Ending "Ful"When a compound noun in the form [container]-"ful", by far the safest option is to add an "s" to the end to form the plural. However, it might be acceptable to add an "s" to the first half of the compound.
Unsure? If you're unsure, add "s" to the end. Sorted.
More technical help? If you're still unsure which version to choose (e.g., "mouthsful" or "mouthfuls"), use Google's Ngram viewer (which searches millions of books for the terms). This tool tells you - in less than a second - how the terms have been used over the last two centuries. Here are some examples:
- bucketsful and bucketfuls (opens a new tab) (This example suggests both versions are acceptable.)
- mouthsful and mouthfuls (opens a new tab) (This example suggests "mouthsful" is wrong but "mouthfuls" is correct.)
- spoonsful and spoonfuls (opens a new tab) (This example suggests "spoonsful" used be acceptable but has been wrong for nearly a century.)
(Rule 7) Forming the Plurals of Compound Nouns with a Noun and a PrepositionWhen a compound noun consists of a noun and a preposition, pluralize the noun.
In these examples, the nouns are in bold.
(Rule 8) Forming the Plurals of Compound Nouns with a Verb and a PrepositionWhen a compound noun consists of a verb and a preposition, add an "s" to the end.
In these examples, the verbs are in bold.