The plural of a noun is formed by adding -s to the end of the noun. For example: boat, plural: boats; chair, plural: chairs; book, plural: books. But if the noun ends in -s, -z, -x, -ch, or -sh then the plural is -es. For example: box, plural: boxes; match, plural: matches; bus, plural: buses.
Nouns ending in -y, if the -y is preceeded by a consonant, form the plural by changing the -y into -ies. For example: city, plural cities. If the -y is preceeded by a vowel, the plural is -ys. For example: monkey, plural: monkeys.
Some nouns that end in -o add -s to form the plural. For example: piano, plural: pianos. Some add -es to form the plural. For example: tomato, plural: tomatoes. Some add either -s or -es. For example: volcano, plural: volcanos or volcanoes.
