Short adjectives: the fixed set you need at A1
рад, до́лжен, за́нят, бо́лен, согла́сен, гото́в, жена́т, за́мужем and наме́рен — predicative only, and they never decline for case.
A group of adjectives has a second, short form that is used only as a predicate — never in front of a noun, and never inflected for case. It has four shapes, masculine, feminine, neuter and plural. The set you need is small and closed: рад, ра́да, ра́до, ра́ды; до́лжен, должна́, до́лжно, до́лжны; за́нят, занята́, за́нято, за́няты; бо́лен, больна́, бо́льно, бо́льны; согла́сен, согла́сна, согла́сно, согла́сны; гото́в, гото́ва, гото́во, гото́вы; наме́рен, наме́рена, наме́рено, наме́рены; жив, жива́, живо́, живы́; винова́т, винова́та, винова́то, винова́ты. Two more are single fixed forms rather than full paradigms: жена́т, said of a man, and за́мужем, said of a woman, both meaning 'married'.
The feminine is where the stress surprises people, and there is no reliable rule to fall back on. До́лжен but должна́. Бо́лен but больна́. За́нят but занята́. Жив but жива́. Against those, ра́да, гото́ва, согла́сна and наме́рена keep the stress on the stem. Learn the four shapes as a unit rather than deriving them, which is easy enough for a list this short.
The syntax is the easy part. The short form sits after the subject with no copula in the present, exactly like every other zero-copula sentence: Я рад, Она́ должна́ уйти́, Мы гото́вы, Он бо́лен, Я согла́сна. With an infinitive it expresses obligation, willingness or intention: Я до́лжен позвони́ть, Мы гото́вы вы́йти, Она́ наме́рена продолжа́ть. Because the short form never takes a case ending, nothing changes around it — Я рад вас ви́деть stays exactly as it is however the other words are inflected.
It is worth understanding why the language keeps both forms. The long adjective is descriptive and can stand in front of a noun: бо́льной ребёнок, за́нятый челове́к. The short form states a condition holding right now, and it cannot go in front of a noun at all: ребёнок бо́лен, челове́к за́нят. The difference is close to English 'the sick child' against 'the child is ill'. Some pairs have drifted apart entirely — ну́жный means 'necessary' while ну́жно is the impersonal 'it is necessary' — and a productive set of short forms (интере́сен, краси́в, ва́жен, вели́к, мал) exists beyond the A1 list, but at this level you only need recognition for those.
Examples
- Я о́чень рад вас ви́деть. I am very glad to see you. Listen in Russian: Slow in Russian: Я о́чень рад вас ви́деть.
- Она́ должна́ уйти́ ра́ньше. She has to leave earlier. Listen in Russian: Slow in Russian: Она́ должна́ уйти́ ра́ньше.
- Извини́те, я за́нят. Sorry, I am busy. Listen in Russian: Slow in Russian: Извини́те, я за́нят.
- Мой брат бо́лен, а де́ти здоровы́. My brother is ill, but the children are well. Listen in Russian: Slow in Russian: Мой брат бо́лен, а де́ти здоровы́.
- Мы согла́сны с ва́шим предложе́нием. We agree with your proposal. Listen in Russian: Slow in Russian: Мы согла́сны с ва́шим предложе́нием.
- Он жена́т, а она́ за́мужем. He is married, and she is married. Listen in Russian: Slow in Russian: Он жена́т, а она́ за́мужем.