Learn Polish: Boi się pan pająków? - Are you afraid of spiders, sir?

The verb bać się (to be afraid) always requires the object you are afraid of to be in the Genitive case. Pająków is the Genitive plural form of pająk (spider).

Where is the word for "of" in this sentence?

You don't need one! In English, we say "afraid of", but in Polish, the verb bać się connects directly to the noun without a preposition. The "of" relationship is already handled by putting the noun into the Genitive case.

Why does this use the third-person verb boi instead of a "you" form like boisz?

The formal word pan (sir / Mr.) always acts as a third-person subject. When you speak formally to a man in Polish, you use third-person grammar, essentially asking "Is the gentleman afraid?" rather than "Are you afraid?".

Why is się placed right after the verb instead of later in the sentence?

The short word się generally prefers to be the second word in a sentence or clause, and it tries to avoid being at the very end. Since this conversational question skips the question word czy and starts right with the verb Boi, się naturally tucks in right behind it.