This is a common feature of Germanic languages. It is a rule called the "verb second" rule. It states that the verb is the second element in the sentence; in this case "måske" is the first element, so the verb "er" must be next. Hope this helped.
Also applies to German - This would translate to "Vielleicht ist er müde" :)
English is also a Germanic language, but we do not do it that way in English. "Maybe is he tired"? does not make much sense. Something to get used to. Thanks for explaining.
As a matter of fact, it happens in English as well through the phenomenon of inversion. "Little did I know that he was tired" could be an altered example of this.
I do not think so
"Er han træt" is a question (is he tired) "Han er træt" is a statement (he is tired) Maybe has nothing to do with it. Remove it and it is still "er" before "han"
Verb before subject is a question Subject before verb is a statement
Does anyone know if it's strict rule? I mean, can i say "måske han er træt"?
Yes it is. 'Måske' and any other phrase/word that is put in the beginning is put for emphasis purposes. Since Danish strictly requires that the verb must be second in order, we have the inversion phenomenon. So it is either "Måske er han træt." or "Han har måske træt." (For the second one I am not sure if måske must be the third ir fourth word, as I am a learner myself. Held og lykke!)
Nop, there is some adverbier (like måske) wich always make the words invert.