Questions & Answers about Þau ganga um bæinn.
Why is the word for town written as bæinn instead of bærinn?
It is because of the preposition um (around). The preposition um always makes the noun that follows it take the accusative case. The basic subject form is bærinn (the town), but in the accusative, the -r- drops out and it changes to bæinn.
Does the preposition um always mean around?
It often means around or through when describing physical movement, like in this sentence. However, it can also mean about when discussing a topic (like a book about Iceland). No matter which meaning you use, um always requires the following noun to be in the accusative case.
Why does the sentence use þau for they?
How do we know the verb ganga translates to are walking instead of just walk?
Icelandic does not have a separate continuous tense like English does. The single verb ganga can mean either walk or are walking depending on the context of the conversation. Here, they are currently in the middle of walking around the town.