One book, two books
A plural count noun usually refers to more than one person or thing. Many English nouns make that change by adding -s: one book, two books; one apple, three apples.
The British Council’s guide to count nouns shows the common patterns. Learning the ending can help you recognise the word even when its spelling changes.
When the ending needs an extra syllable
A box becomes boxes, a wish becomes wishes and a watch becomes watches. Many nouns ending in -s, -x, -sh or -ch take -es.
These examples are useful patterns, not a substitute for checking an unfamiliar word. English has exceptions, and a dictionary can settle the form when the ending does not behave as expected.
Baby becomes babies; boy becomes boys
Look just before a final y. After a consonant, a common pattern is to replace y with -ies: baby → babies and country → countries.
After a vowel, keep the y and add -s: boy → boys and day → days. The last letter alone does not tell the whole story.
Some words change inside
Child becomes children, foot becomes feet and woman becomes women. These common irregular plurals need their own forms; adding -s will not produce the usual plural.
A plural ending is one job that a suffix can do. For a word made from more than one part, look at compound words. Ask what the whole word means before deciding how to change it.