Three genders, one rule
Russian nouns belong to one of three genders. You almost always know the gender just by looking at the last letter. This matters because adjectives, possessives, and verbs in the past tense will agree with the noun.
The endings
Masculine: ends in a consonant. Examples: дом, кот, стол, друг, чай. Feminine: ends in -а or -я. Examples: мама, книга, песня, семья. Neuter: ends in -о or -е. Examples: окно, молоко, море, поле.
The soft sign trap
Nouns ending in -ь (the soft sign) can be either masculine or feminine — you have to memorize them. Common ones: день (day, masculine), ночь (night, feminine), мать (mother, feminine), словарь (dictionary, masculine).
Why gender matters
Possessive pronouns and adjectives change form to match. 'My cat' vs 'my book' won't be the same word for 'my'. You'll see this in lesson 7.
How to look up gender
In any dictionary, the last letter of the dictionary form (the nominative singular) almost always tells you. When it doesn't (i.e., -ь nouns), the dictionary marks it: м for masculine, ж for feminine.
