Free Collins Cobuild English Grammar by Collins

compound noun is a countable noun, the plural form of the countable noun is used when the compound noun is plural.
Air raids were taking place every night.
… health centres , banks, post offices , and police stations .
Loud voices could be heard through letter boxes .
…the refusal of dockers to use fork-lift trucks .
    For full information about the plural forms of countable nouns, see the Reference Section.
    Compound nouns that are directly related to phrasal verbs usually have a plural form ending in -s .
Nobody seems disturbed about cover-ups when they are essential to the conduct of a war.
Naturally, I think people who drive smarter, faster cars than mine are show-offs .
    A few compound nouns are less directly related to phrasal verbs, and consist of a countable noun and an adverb. In these cases, the plural form of the countable noun is used before the adverb when the compound noun is plural.
    For example, the plural of runner-up is runners-up , and the plural of summing-up is summings-up .
Passers-by helped the victim, who was unconscious.
    Compound nouns that consist of two nouns linked by the prepositions of or in , or a noun followed by to-be , have a plural form in which the first noun in the compound is plural.
I like birds of prey and hawks particularly.
She was treated with contempt by her sisters-in-law .
Most mothers-to-be in their forties opt for this test.
    Some compound nouns have been borrowed from other languages, mainly French and Latin, and therefore do not have normal English plural forms.
Agents provocateurs were sent to cause trouble.
The nouveaux riches of younger states are building palatial mansions for themselves.
1.92     Compound nouns are fixed expressions. However, nouns can always be used in front of other nouns in order to refer to something in a more specific way. For the use of nouns as modifiers , see paragraphs 2.169 to 2.174 .
    Talking about people and things without naming them: pronouns
1.93     When you use language, both in speech and writing, you constantly refer to things you have already mentioned or are about to mention.
    You can do this by repeating the noun phrase, but unless there is a special reason to do so, you are more likely to use a pronoun instead.
    Pronouns make statements less repetitive.
John took the book and opened it .
Deborah recognized the knife as hers .
Shilton was pleased with himself . This is a very busy place.
    However, if you have mentioned two or more different things, you usually have to repeat the noun phrase to make it clear which thing you are now talking about.
Leaflets and scraps of papers were scattered all over the floor. I started to pick up the leaflets .
I could see a lorry and a car. The lorry stopped.
    For other ways of talking about things that have already been mentioned, see paragraphs 10.2 to 10.39 .
    types of pronoun
1.94     There are several different types of pronoun:
    personal pronouns . See paragraphs 1.95 to 1.106 .
    possessive pronouns . See paragraphs 1.107 to 1.110 .
    reflexive pronouns . See paragraphs 1.111 to 1.118 .
    generic pronouns . See paragraphs 1.119 to 1.123 .
    demonstrative pronouns . See paragraphs 1.124 to 1.127 .
    indefinite pronouns . See paragraphs 1.128 to 1.141 .
    reciprocal pronouns . See paragraphs 1.142 to 1.145 .
    relative pronouns . See paragraphs 1.146 to 1.150 .
    interrogative pronouns . See paragraphs 1.151 to 1.153 .
    There are a few other words that can be used as pronouns. For more information about these, see paragraphs 1.154 to 1.161 .
    Talking about people and things: personal pronouns
1.95     You use personal pronouns to refer to yourself, the people you are talking to, or the people or things you are talking about.
    There are two sets of personal pronouns: subject pronouns and object pronouns.
    subject pronouns
1.96     Subject pronouns refer to the subject of a clause.
    Here is a table of subject pronouns:
 
singular
plural
1st person
I
we
2nd person
you
3rd