Learn Finnish: Onkohan isoisän arkussa aarre vai romua? - I wonder if there is a treasure or junk in grandfather's chest?

The verb on means 'is'. Adding the question particle -ko makes it onko ('is there?'). Adding the suffix -han softens it into a thought you are pondering. Together, onkohan perfectly translates to 'I wonder if there is'.

Why is aarre in the basic form while romua is in the partitive case?

This is an existential sentence (stating what exists inside a location). In these sentences, singular countable nouns like aarre (a treasure) take the basic nominative form. However, uncountable mass nouns like romu (junk) must take the partitive case, becoming romua.

Why use vai instead of tai for 'or'?

In Finnish, vai is strictly used for 'or' in questions where you are presenting mutually exclusive options and expect a choice between them (is it A, or is it B?). Tai is used for 'or' in regular statements. Since this sentence is a question offering two distinct alternatives, vai is required.

What is the base form of arkussa, and why did the spelling change?