Because when speaking about objects, things, and places (not people), Russians pay attention to the endings of these nouns. They divide singular nouns (nouns naming one object, thing, or place) into three categories: masculine, feminine, and neuter. These categories are called grammatical genders.

Nouns that belong to the masculine gender usually end with a consonant: дом, торт, кот. Nouns that belong to the feminine gender usually end with -а or -я: семья, планета, книга. Nouns that belong to the neuter gender usually end with -o or -e: окно, письмо, море.

There are a few exceptions to this rule - we will learn them in the next course.