Adjectives: genders
In Russian adjectives almost always precede nouns (like in English). They are conjugated according to the gender of the noun that follows them. Compare:
большой дом = a big house
большая собака = a big dog
большое письмо = a big letter
The adjectives that precede masculine nouns end in "ой", "ий" or "ый": хороший (good), высокий (tall), добрый (kind), синий (blue).
The adjectives that precede feminine nouns end in "ая" or "яя": хорошая (good), высокая (tall), добрая (kind), синяя (blue).
The adjectives that precede neuter nouns end in "ое" or "ее": высокое (tall), хорошее (good), доброе (kind), синее (blue).
Practice
Look and listen:
большой = big (masculine)
большая = big (feminine)
большое = big (neuter)
хороший = good (masculine)
хорошая = good (feminine)
хорошее = good (neuter)
высокий = tall (masculine)
высокая = tall (feminine)
высокое = tall (neuter)