The document discusses plural nouns in English. It explains that most nouns form the plural by adding -s, but there are exceptions. Nouns ending in consonant + y change the y to i and add -es. Nouns ending in a vowel + y just add -s. Nouns ending in s, x, z, ch, sh add -es. Nouns ending in f or fe change to -ves. There are also irregular plural forms that do not follow rules like mouse/mice and woman/women. The document also discusses countable vs. uncountable nouns and provides examples of each category.