Compound noun:
Noun + noun = bedroom, water tank, motorcycle, printer cartridge, chairmanNoun + verb = rainfall, haircut,
Verb + noun= washing machine, driving license, swimming pool
Pluralization of compound nouns
Rule one: Pluralize the significant word
Examples: a. Attorney general = Attorneys general.
b. Brigadiar-general = Brigadier-generals
c. Order-in-council = orders-in-council
d. Assistant chieg of staff = Assistant chiefs of staff
d. Poet laureate = Poets laureate
Rule two: Pluralize both if both words are equally significant.
a. Man driver = Men drivers
b. Woman writer = women writer
Rule three: Add -s- after the word when no word is significant in itself.
Examples:
a. Trade union = trade unions
b. Judge advocate = judge advocates
Rule four: If any noun is hyphenated with a preposition, the plural is formed on the noun.
Example:
Filler-in = fillers-in
Passer-by = passers-by
Hanger-on = hangers-on
Maker-up = makers-up
Rule five: If any verb is hyphenated with a preposition, the plural is formed on the preposition.
Examples: Check-in = Checksins
Build-up = Build-ups
Love-in = Love-ins
Rule six: add -s- to nouns ending in 'full'
Examples:
Teaspoonful = teaspoonfuls
Cupful = Cupfuls
Handful = handfuls
Sackful = sackfuls
Rule seven: when you've word like 'man of honor', the first word is the principal word. So, you have to pluralize the first word.
Examples:
Man of honor =Men of honor
Cup of coffee = Cups of coffee
Man of peace = Men of peace