ότι

In a sentence

• Πιστεύω ότι θα έρθει σύντομα.

  I believe that he will come soon.

  Here, "ότι" is used to introduce a subordinate clause that provides additional information, in this case, the subject of the belief.

• Κατάλαβα ότι έκανες λάθος.

  I understood that you made a mistake.

  In this sentence, "ότι" is used to connect the main clause with the direct object, explaining what was understood.

• Σου είπα ότι είμαι κουρασμένος.

  I told you that I am tired.

  Here "ότι" serves to introduce the content of what was told in the main sentence, functioning as a conjunction to connect clauses.