1. Adjectives in Russian language have:

— three genders: masculine, feminine, neuter;
— two numbers: singular, plural;
— degrees of comparison;
— declension;
— 6 cases.

The gender, number and case of the adjective is determined by the gender, number and case of the modifying noun. In the dictionaries you will be given a masculine singular form of an adjective.

2. Gender and number

Adjectives of masculine gender have -ой, -ый, -ий endings.
Adjectives of feminine gender have -ая, -яя endings.
Adjectives of neuter gender have -oe, -ее endings.
In the plural all adjectives have the endings -ые, -ие in the nominative case.

3. There are descriptive, relative and possessive adjectives.

1) Descriptive adjectives denote the quality and features of an object: красивый – beautiful, дорогой – expensive, холодный – cold, теплый – warm, молодой – young.

Descriptive adjectives have:
a) two forms: full (красивый) and short (красив). Short forms change by gen¬der and number (красив — т., красива — f., красивы — pl.), but not by case.
b) degrees of comparison:
— analytical: молодой — более молодой — самый молодой;
— suffixal: красивый — красивее — красивейший;
— suppletive: хороший — лучше — наилучший;
c) adjective adverbs: тепло, холодно, красиво.

2) Relative adjectives denote the characteristics relative to some other object, action or attitude:
Молочный коктейль — milk shake, апельсиновый сок – orange juice, working hours – рабочие часы, деловая встреча – business meeting. These adjectives have no degrees of comparison.

3) Possessive adjectives denote ownership of an object: невестино кольцо – bride’s ring, Наташин дом — Natasha's house. These adjectives have no degrees of comparison.