kupiła

In a sentence

• Maria kupiła książkę.

  Maria bought a book.

  Here, 'kupiła' is used as a past tense verb in the third person singular form to indicate an action of purchase that Maria completed.

• Wyjaśniła, że kupiła to wczoraj.

  She explained that she bought it yesterday.

  In this sentence, 'kupiła' is a part of a dependent clause, referring to a purchase done in the past that is being explained.

• Czy już kupiła tę sukienkę?

  Has she already bought that dress?

  'Kupiła' here is used in a question form to inquire about whether the act of buying has been completed by the female subject.