þá

In a sentence

• Við hittumst þá sem við vorum í skólanum.

  We met then when we were in school.

  Here, 'þá' is used to specify the time period during which the meeting took place, acting as a temporal adverb.

• Við munum fara þangað ef veðrið verður gott, og þá getum við líka heimsótt safnið.

  We will go there if the weather is good, and then we can also visit the museum.

  In this case, 'þá' illustrates the sequence of events, functioning again as a temporal adverb.

• Ég sá að þeir höfðu misst boltann, þá tók ég hann upp og gaf þeim hann.

  I saw they had lost the ball, so I picked it up and gave it to them.

  Here, 'þá' connects clauses, essentially meaning "so" or "therefore," showing a causal or logical consequence.