NUMBER OF NOUNS

Number of Nouns

An English noun can be singular or plural in number.

1. Generally speaking, a singular noun becomes plural by adding 's' to is, such as persons, girls, dogs, cats, books, chairs, etc.  Many common nouns become plural in this way.
2. But a large number of other common nouns do not form their plural number by adding 's', but by adding 'es', 'ies', or 'ves'.  Some examples are hero-heroes, church-churches, lady-ladies, city-cities, shelf-shelves, wife-wives. Other irregular methods are seen in words like man-men, tooth-teeth, child-children.

Examples:

#     He is a nice man. Have you come across nice men?

note : come across is an idiom which means meet/find by chance.