Number

If man in a compound noun in singular word does not refer to a human,only "s" should be added after the  word to make it in plural form.i.e.

singular.........................plural

German......................Germans

Norman......................Normans

Mussalman...............Mussalmans

Brahman.....................Brahmans

9)If there is full with a singular compound noun,only "s" is added to make it a plural noun.i.e.

singular.........................plural

Handfull.......................Handfulls

Spoonfull...................Spoonfulls

Mouthfull...................Mouthfulls

10)If a compound noun has many parts,the main part of it should be turned into plural word.i.e.

singular........................................plural

Brother-in-law.........................Brothers-in-law

Father-in-law..........................Fathers-in-law

Mother-in-law........................Mothers-in-law

Passer-by..............................Passers-by

Step-brother..........................Step-brothers

Maid-servant.........................Maid-servants

Commander-in-chief...........Commanders-in-chief

Book-case.............................Book-cases

Book-shelf............................Book-shelfs

Forget-me-not.......................Forget-me-nots

Poet-laurete..........................Poet-lauretes

Major-general.......................Major-generals

Number

To change a singular number word into a plural number word ,there are some other rules.They are:-

6) sometimes,plural words can be formed by changing any vowel in some singular words i.e.

singular....................plural

man.........................men

woman.....................woman

foot..........................feet

goose......................geese

mouse......................mice

louse.......................lice

tooth.......................teeth

7)Plural words can be made by adding en/ren/ne after singular words.i.e.

singular....................plural

ox............................oxen

child.......................children

brother...................brothers/brethren

cow........................kine/cows

8)If a compound noun ends with man which refers to any human being,it can be turned into plural form by changing a vowel in man .i.e.

singular....................plural

fisherman.............fishermen

boatman............boatmen

workman...........workmen

salesman...........salesmen

milkman...........milkmen

man-of-war....men-of-war