Rule 7 - If the noun which is formed by compound and that has one portion is preposition then to make that plural we add ‘s’ which comes before the preposition. For example: Father-in-law - Fathers - in - law, Passer- by - Passers – by.

Rule 8 - If the compound noun has man or woman then to make that plural we need to add ‘s’ in the whole. For example: Man - servant → Men - servants, Woman - engineer → Women - engineers.

Rule 9 - If we use Police then it is a plural noun but if we use man in Police then it will be known as a singular noun. For example: Police are corrupt. (But the) Police man is honest