No, not regional at all. It just that at different times different words become fashionable in Ukrainian. People forget about alternatives and start to misuse certain words.
So we have this three verbs in Ukrainian: мати, повинен, мусити. The first is the least strong one, the last is the most.
When you have some need to do something or something will happen because it has to happen you use мати:
- Я маю йти
- Завтра має бути спекотно
(well now I should choose proper English translation and I can't :( )
When there's an obligation you use повинен.
And you use мусити when you really have to do something, someone is making you do something, it's really important to do that even though you may not want to do that/would rather not do that.
But people often just say what they feel like saying. There've a been a big increase in popularity of повинен because it's a direct translation of Russian должен and in Russian there's only that one word. So some forgot that Ukrainian also have others
Thank you for such a long and detailed explanation.
I would translate as: Я маю йти - I should go.
I actually use повинен to mean "have to" and мусити as "must" (there is no recourse).
Interesting that you used йти in your example, the lesson used іти. I actually had to go back and change it for the answer to be correct.
Завтра має бути спекотно - it should be hot tomorrow. Is Kyiv having the same heatwave as western Europe?