1) Generally, long-form adjectives refer to general qualities of a subject, while short adjectives are used to describe temporary quality or condition. For example: Он больной -- He is ill (= He has some permanent, chronic or serious illness) Он болен -- He is ill (right how / at the moment / today etc), He is feeling unwell (eg.: Он болен и не может сегодня поехать на работу) 2) The short adjectives dont have case forms and they are almost always used as a predicate and can’t be used as an attribute: Эта девушка очень красива (predicate) (''Эта девушка очень красивая'' is possible as well) but: Я вижу красивую девушку (attribute) 3) In colloquial spoken language the long adjectives are usually used

«Красивая» and «красива» mean the same, but have different subtle «taste». Native russian speakers use them in different ways. For example: «Эта девушка красивая» - just ascertaining of the fact with minimum emotions in words. «Как красива эта девушка!» - brings some sort of admiration with beauty of girl. «Красивая» - more common feminine form, so before you will understand in which satiation «красива» will be more pertinent, better use «красивая». :) P.S. I only learn to write in English, so maybe made a lot of mistakes. Will be thankful for corrections!

Красивая - полное прилагательное Красива - краткое прилагательное Значение абсолютно одно и то же

Both forms are feminine.