What kind? Adjectives

One word, four endings

A Russian adjective copies its noun: in the singular it changes for gender, and in the plural it has one form for everything. Dictionaries print the masculine, so новый is the word you learn, and новая, новое, новые are that same word dressed for the noun beside it. Notice the plural – a single ending for all three genders, exactly like мои.

Какой? – the question that asks for a description

Какой? asks what kind of?, and being an adjective itself it agrees too: Какой это дом? Какая это книга? Какое это окно? Какие это дома? The answer repeats the ending of the question, which makes the question the quickest way to check that you picked the right form.

Это новый дом, а это старые дома.This is a new house, and these are old houses.

-ый, -ой or -ий

Three things decide the masculine ending. When the stress falls on the ending itself, it is -ой: большо́й, плохо́й. When the stem ends in one of к, г, х, ж, ч, ш, щ, the letter ы is forbidden, so you write -ий in the masculine and -ие in the plural: хороший – хорошие, маленький – маленькие. Everything else is the plain -ый / -ые.

Какие это книги? – Хорошие и интересные.What kind of books are these? – Good and interesting ones.