This is the first part of the lesson. The rest, the exercises and the reviews are in the app.
Relative pronouns: koji, one word for who, which and that
To hook an extra clause onto a noun, English gives you a choice of three words: who for people, which for things, that for either. Serbian manages with one: koji. It links the main statement to the clause that tells you more: “the man who works”, “the book that I am reading”, “the city in which I live”.
You already know koji as a question word, “which?” (the lesson “Interrogative pronouns”). Now it takes on a second, relative job, just as English who and which both ask and link. The key question of this lesson: where does koji get its case from?
The main law: gender from the noun, case from the clause
koji answers to two masters. It takes its gender and number from outside, from the noun it refers to: čovek (man) makes it masculine, žena (woman) feminine, ljudi (people) plural. It takes its case from inside, from its job in the relative clause: subject means nominative, direct object accusative, indirect object (“to whom”) dative, and after a preposition whatever case the preposition demands.
Formal English keeps a trace of this: the man who works, but the man whom I see. Who and whom are case forms chosen by the clause, not by “the man”. Serbian does this every time, for every gender, for things as well as people.
The noun is always čovek, masculine singular, yet koji changes (kojeg, kome, kojim) because each time it fills a different slot in its own clause.
All genders, all cases
Feminine, neuter and plural follow the same law. Here is the working set of forms of koji; it declines like moj and svoj, which you already know (the lesson “Possessive pronouns”):
The pairs kojeg and koga, kojem and kome are both everyday forms, equally correct in speech and in writing. In quick speech you will also hear the short kog and kom, while the full kojega and kojemu sound bookish. The locative (after u and na of place, and after o, “about”) has the dative forms: u kojem or u kome, u kojoj.
Animacy: kojeg / koga or koji
One subtlety, in the masculine only. In the accusative, koji behaves exactly like a masculine noun (the lesson “Animacy”) or like moj: with an animate noun (a person or an animal) the accusative looks like the genitive (kojeg or koga); with an inanimate one (a thing) it looks like the nominative (koji).
Cheat sheet
The cheat sheet — everything essential from the lesson on one page. In the app it opens at any time.