þessa

In a sentence

• Ég fékk þessa bók frá móður minni.

  I received this book from my mother.

  The word 'þessa' is used here as an accusative singular feminine to modify the noun 'bók' (book).

• Ég sé þessa menn á torginu.

  I see these men in the square.

  In this sentence, 'þessa' is accusative plural of 'þessir' used to modify the plural noun 'menn' (men).

• Við munum heimsækja þessa staði á morgun.

  We will visit these places tomorrow.

  Here, 'þessa' functions as the accusative plural of 'þessi' to modify the plural noun 'staði' (places).