"Is this Hungarian or Finnish?"
Translation:Onko tämä unkaria vai suomea?
/tai/ is inclusive OR (i.e. this, that, or both), whereas /vai/ is exclusive OR (this or that, but not both).
The Wiktionary example is also quite useful: Söitkö sinä leivän tai hedelmät? - have you eaten bread or fruit (or both, or neither), vs Soitkö sinä leivän vai hedelmät? - did you eat bread or fruit (in a sense of, which of these two have you eaten; the "both" and "neither" are not acceptable answers here)