This is the 33rd most frequent Icelandic word.
þau
The Icelandic word "þau" is a pronoun meaning "they" (used for mixed-gender or neuter groups).
The word "þau" is used as a nominative plural pronoun referring to a group of mixed genders or indeterminate gender composition.
Þau eru vinir okkar.
They are our friends.
In this sentence, "þau" is the accusative plural form of the pronoun, used to refer to a group as the object of the sentence.
Við sáum þau í bænum í gær.
We saw them in town yesterday.
Again, "þau" here functions as a nominative plural pronoun referring to people engaged in the action of learning Icelandic.