Я купил несколько книг для твоего семинара.

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Breakdown of Я купил несколько книг для твоего семинара.

• книга: the book
• купить: to buy
• для: for

Questions & Answers about Я купил несколько книг для твоего семинара.

Why is the verb купил used here instead of покупал?

Russian verbs come in pairs of imperfective and perfective aspect. Купил is the perfective past, showing a completed action: “I bought (and finished buying) those books.” Покупал is imperfective, which would mean “I was buying” or “I used to buy,” focusing on the process or habitual past without implying completion.

Why does несколько require the genitive case, giving несколько книг rather than несколько книги or несколько книга?

The quantifier несколько (“several/few”) always governs the genitive plural of the noun that follows. That’s a fixed rule: after несколько, you decline the noun in genitive plural, hence книг.

Why is книг in genitive plural rather than nominative книги or another case?

Because of the combination with несколько, the noun must be in genitive plural. This is sometimes called a “partitive genitive” when expressing an indefinite quantity. So несколько (чего?) — книг.

Why is the phrase для твоего семинара in genitive case? Wouldn’t “для” use the dative?