Скажи мне, зачем тебе новая куртка?

Tell me why you need a new jacket.

Breakdown of Скажи мне, зачем тебе новая куртка?

• я: I
• новый: new
• куртка: the jacket
• ты: you
• зачем: why
• сказать: to tell

Questions & Answers about Скажи мне, зачем тебе новая куртка?

What exactly does зачем mean, and how is it different from почему?

Зачем literally means “for what purpose” or “why (in order to…).” It asks about the goal or purpose behind an action. Почему means “why” in the sense of a cause or reason.
Example:
– Зачем ты купил книгу? (“What’s the purpose of buying the book?”)
– Почему ты купил книгу? (“What’s the reason you bought the book?”)

Why is тебе in the dative case here?

In the full version of the underlying clause, Russian uses the structure мне нужна книга (“I need a book”), where мне is dative. Our sentence omits нужна, but keeps the same syntax:
– Скажи мне, зачем тебе новая куртка (нужна)?
So тебе remains dative because it marks the person who needs something.

If тебе is dative, why is новая куртка in the nominative instead of the accusative?

Again, this comes from the “нужна” construction. In мне нужна куртка, куртка is the grammatical subject and stays in the nominative. The person needing (мне/тебе) is in the dative. Since we dropped the verb нужна, новая куртка remains nominative.

Why is there a comma after Скажи мне?

The comma separates the main clause (Скажи мне) from the subordinate clause introduced by зачем. In Russian, any subordinate clause after a verb of speech or thought is set off by a comma.

What part of speech is Скажи in this sentence?

Скажи is the imperative (command) form of сказать (“to say” or “to tell”). Скажи мне means “tell me” or “say to me.”

Could you replace зачем with для чего here?

Yes. Для чего is more formal/literary but has almost the same meaning: “for what purpose.”
– Скажи мне, для чего тебе новая куртка?

Is the word order flexible? Could I say “Скажи мне зачем новую куртку тебе”?

Russian word order is relatively free, but some orders sound awkward. The most natural order is:
– Скажи мне, зачем тебе новая куртка?
Moving тебе to the end (зачем новую куртку тебе) is understandable but less idiomatic.

I noticed there’s no verb in the subordinate clause. Is that common?

Yes. Russian often omits the predicate in clauses with нужен/нужна/нужно, especially in questions. The full thought is зачем тебе новая куртка нужна?, but dropping нужна makes the question shorter and more conversational.