þessar

In a sentence

• Ég tók þessar bækur af borðinu.

  I took these books off the table.

  In this sentence, "þessar" is used as a demonstrative pronoun in the accusative case plural form to refer to the books.

• Ertu búinn að sjá þessar bíómyndir?

  Have you seen these movies?

  Here, "þessar" is again a demonstrative pronoun in the plural form, modifying the noun "movies".

• Það eru þessar stelpur sem skemmtu sér vel.

  It is these girls who had a good time.

  In this example, "þessar" functions as an identifying modifier providing specific identification of the subjects.