zein

zein asks which. It asks the listener to choose from a group that both people have in mind:

• Zein da zure etxea? Which one is your house?
• Zein nahi duzu? Which one do you want?
• Zein da zure izena? What is your name?

English says what in the last question, but Basque treats a name, a phone number or an address as one item picked from many, so it uses zein. You can also ask Nola duzu izena? See nire izena ... da.

zein + noun. zein comes before the noun, and the noun takes no article, just as after a number: Zein liburu nahi duzu? (Which book do you want?), Zein autobus doa Donostiara? (Which bus goes to Donostia?). See number + noun without article.

Next to the verb. zein, together with its noun, stands right before the verb: Zein kolore gustatzen zaizu? (Which color do you like?). See question word before the verb.

Case endings. zein takes the ending the sentence needs. As the doer of a transitive verb it becomes zeinek: Zeinek irabazi du? (Which one has won?). With a noun, the ending goes on the noun: Zein herritan bizi zara? (Which town do you live in?). These endings come in indefinite case forms (mugagabea). For several items you can keep zein or use zeintzuk, which is common especially in the west: Zeintzuk dira zure liburuak?

zein or zer? Use zer for an open question with no list to choose from: Zer egiten duzu? Use zein to pick from a set: Bi liburu daude. Zein nahi duzu? (There are two books. Which do you want?). Some questions allow both, and for open questions such as Zer ordutan? the Academy prefers zer. See zer.

Exclamations. Before an adjective, zein can also mean how: Zein polita! (How pretty!). See hain, horren and exclamations.