opnað

In a sentence

• Ég hef opnað gluggann.

  I have opened the window.

  The word 'opnað' is used here as the past participle form of the verb 'opna', following the auxiliary verb 'hef', to indicate a completed action in the perfect tense.

• Bókin var opnuð af kennaranum.

  The book was opened by the teacher.

  In this sentence, 'opnuð' (a derived form of 'opnað') is used in the context of a passive voice construction to describe the book being in an opened state caused by the teacher.

• Við skulum opna dyrnar.

  Let us open the doors.

  Here, the verb 'opna' is in its infinitive form, following the modal verb 'skulum', to suggest a proposal to perform the action of opening.