Learn Finnish: Tällä pölyisellä ullakolla on kummitus. - There is a ghost in this dusty attic.

In Finnish, certain locations conventionally take the adessive case (-lla / -llä, usually meaning "on") rather than the inessive case (-ssa / -ssä, meaning "in"). Words for attics (ullakko), yards (piha), and markets (tori) are classic examples. You simply have to memorize that you use ullakolla even though the English translation says "in the attic".

How does the adjective pölyisellä get its form?

It comes from the basic adjective pölyinen (dusty), which is derived from the noun pöly (dust). Finnish words ending in -nen change their stem to -se- before adding case endings. Because adjectives must agree with the noun they describe, it takes the same adessive -llä ending as ullakolla, giving us pölyisellä.

This lesson is about the wondering clitic -kohan / -köhän. How would I change this sentence to mean "I wonder if there is a ghost in this dusty attic?"

You would attach -kohan to the verb on and move it to the very front of the sentence. This fuses the question clitic -ko (turning the statement into a yes/no question) with the softening clitic -han (adding the "I wonder" tone). The new sentence becomes: Onkohan tällä pölyisellä ullakolla kummitus?

Why is the subject kummitus at the very end of the sentence?