Breakdown of Ég ætla að athuga hvort búðin er opin.
ég
I
búðin
the shop
opinn
open
að
to (infinitive marker)
Questions & Answers about Ég ætla að athuga hvort búðin er opin.
Why do we use hvort here instead of ef (if)?
In English, we often say 'check if the shop is open'. But in Icelandic, when you form an indirect yes/no question (where the underlying question is 'Is it open?'), you must use hvort (whether). The word ef is strictly used for 'if/then' conditions, like 'I will go if it is open'.
Does the word order change after hvort?
No, the word order in the indirect question hvort búðin er opin stays exactly like a normal statement: Subject (búðin) + Verb (er) + Adjective (opin). You do not flip the subject and verb here.
Why is the word for 'open' written as opin instead of opið?
Opin is an adjective describing the shop (búðin). Since búð is a feminine noun and is the subject of this clause, the adjective must be in the feminine nominative form, which is opin. If you were checking on a neuter noun like a museum (safnið), it would be opið.
Just as a refresher, why is there an að before athuga?
The verb ætla (to intend / to be going to) is always followed by að plus the infinitive (dictionary) form of the next verb. Together, ætla að athuga means 'am going to check'.