Adjectives

Adjectives are special words for describing nouns.

Хороший человек –  nice person
Отличная погода – good weather

The same adjective may have 3 variants of  endings:

красивый
красивая
красивое
красивые

All these 4 words mean “beautiful“. So you may ask, what’s the difference between them.  The difference is only that Russian adjectives always match with nouns they’re describing. If you’re describing a masculine gender noun you need to use a masculine ending for adjectives (-ый / -ой / -ий). For describing feminine nouns you need to use feminine  endings for adjectives (-ая /-яя).

Красивый мужчина – a handsome man
Красивая девушка – a beautiful girl

For example:

телефон (он) – a telephone (he)
машина (она) – a car (she)
окно (оно) – a window (it)

And when we have an adjective to describe a noun it has to be matched with the noun. It will be:

красивый телефон – a beautiful phone (he)
красивая машина – a beautiful car (she)
красивое окно – a beautiful window (it)