We need the か particle to form “or”. In its simplest form:
|Tea or coffee.|
For more complicated structures we can think it as a set of embedded questions. We already saw how to embed a question in a sentence here.
|I don’t know if the teacher is kind.|
All we’re doing now is adding another embedding question using the same grammar.
|I don’t know if the teacher is kind or unkind.|
|I can’t decide whether to buy chocolate or flowers.|
|I don’t know if she’s a departmental head or a divisional head.|
|Yusuke||This weekend I’m going camping with friends and will have a BBQ.|
|Yusuke||Well, either that or relax at home.|
Just like when we looked at the casual form of a question for na-adjectives and nouns, we may see なのか used instead of just か to form the structure.
|Let’s ask the waiter whether this is chicken or beef.|
Additionally, you may hear それとも used inside the question clause. This does not change the meaning, merely places emphasis on it being either A or B.
|I don’t know if that’s a bird or a plane.|