English nouns ONLY change from singular to plural.

To create the plural form from the singular for most English nouns, you just add an 'S':

 

SINGULAR	PLURAL
BOOK	BOOKS
PEN	PENS
TABLE	TABLES
BOY	BOYS
GIRL	GIRLS
CAR	CARS
DAY	DAYS

In certain cases, the plural form is created by adding 'ES':

WORDS ENDING IN 'Y'

When the singular noun ends in a VOWEL + Y, then the plural is formd vby adding 'S'

SINGULAR: MONKEY PLURAL: MONKEYS

SINGULAR: ENEMY PLURAL: ENEMIES

In certain cases, a noun will have an irregular plural form. Some of the most common are:

SINGULAR changes to PLURAL

MAN changes to MEN

WOMAN changes to WOMEN