kuris / kuri

Choosing from a group. Use kuris when the options are known: Kuri knyga tavo – raudona ar mėlyna? (Which book is yours, the red one or the blue one?) Use koks when you ask about the kind or quality: Kokią knygą skaitai? (What kind of book are you reading?)

The forms.
kuris, kurio, kuriam, kurį, kuriuo, kuriame · kuri, kurios, kuriai, kurią, kuria, kurioje
Plural: kurie, kurių, kuriems, kuriuos, kuriais, kuriuose · kurios, kurių, kurioms, kurias, kuriomis, kuriose

Following the noun's case. The question word takes whatever case its noun needs: Kuriame name gyveni? (Which building do you live in? – locative), Kuriam draugui skambini? (Which friend are you calling? – dative), Su kuriuo draugu eini? (Which friend are you going with? – instrumental).

Which of you. Use iš with the genitive plural to name the group: Kuris iš jūsų kalba lietuviškai? (Which of you speaks Lithuanian?) Kurią iš šių suknelių pirksi? (Which of these dresses will you buy?)

Which in order. To ask about a position in a row, such as a floor or a time, Lithuanian also uses kelintas: Kelintame aukšte gyveni? See ordinal numbers. Kuris also joins relative clauses, as in knyga, kurią skaitau (the book that I am reading).