1) Plural formation of a noun generally is made by adding ‘s’ to the singular.
Cat, cats; pencil, pencils
Day, days; desk, desks
2) Plural formation of a noun ending in y following a consonant is made by
changing y into ies
City, cities; country, countries;
Fly, flies; pony, ponies
3) Plural formation of noun ending in ch, sh, ss or x is made by adding es.
Church, churches; match, matches
Dish, dishes; brush, brushes;
Class, classes; glass, glasses;
Tax, taxes; box, boxes.
4) Plural formation of most nouns ending in o also is made by adding es.
Buffalo, buffaloes; hero, heroes
Tomato, tomatoes; potato, potatoes.
5) But plural formation of foreign origin or abbreviation ending in o is made by adding only s.
Kilo, kilos; photo, photos
Ratio, ratios; solo, solos.
6) Plural formation of nouns ending in f or fe is made by adding ves.
Shelf, shelves; loaf, loaves;
Thief, thieves; wife, wives;
But there are some exceptional nouns which are made by adding only s.
Handkerchief, handkerchiefs; dwarf, dwarfs;
Safe, safes; strife, strifes.
7) Plural formation of a few nouns is made by adding en.
Child, children; ox, oxen.
Exceptions of Plural formation Number