Breakdown of Кто-нибудь разбил окно на кухне?
окно
window
на
on, at / by (transport) / to (a place) / to (in answer to)
кухня
kitchen
кто-нибудь
anyone / someone (unspecified)
Questions & Answers about Кто-нибудь разбил окно на кухне?
Why is кто-нибудь used here instead of кто-то?
In Russian, the suffix -нибудь is used when the person or thing is completely unknown or hypothetical, which makes it the standard choice for open questions. If you used кто-то, it would imply you believe a specific person broke it, and you're just pointing it out. Кто-нибудь translates closer to 'Did anyone break the window?'
Why is the verb разбил in the masculine form if we don't know who broke the window?
Grammatically, the question word кто (and its derivatives like кто-нибудь) is always treated as masculine singular. The verb must take the masculine past tense ending -л, even if the actual person who broke the window turns out to be a woman or a group of people.
Why use the perfective verb разбил here instead of the imperfective?
You are asking about a single, completed action that has a visible result in the present: the window is currently broken. The perfective aspect (разбить) focuses exactly on this successful completion and its result.
Why do we say на кухне instead of в кухне for 'in the kitchen'?
For a few specific indoor spaces, Russian traditionally uses the preposition на instead of в to indicate location. Кухня is one of the most common exceptions, so 'in the kitchen' is almost always на кухне.