Learn Turkish: Terasında jakuzi olan odalar çok pahalı. - The rooms that have a jacuzzi on their terrace are very expensive.

In Turkish, possession is typically expressed with the existential word var (there is). For example, Terasında jakuzi var means "There is a jacuzzi on its terrace" (or "It has a jacuzzi"). Because var cannot take relative clause suffixes, we replace it with olan (the relative form of olmak) to act as an adjective. So, terasında jakuzi olan odalar literally translates to "the rooms where there is a jacuzzi on its terrace."

Let's look at terasında. Why is it used here instead of just terasta?

Terasında contains the possessive suffix -ı (meaning "its") followed by the buffer letter -n- and the locative suffix -da ("on"). It specifically links the terrace to the room: "on its terrace." If you used terasta, it would mean "on the terrace," which sounds like a shared or public terrace rather than a private one belonging to the room itself.

Why use the subject participle olan instead of an object participle like olduğu?

Whenever you convert a var (there is) or yok (there is not) statement into a relative clause modifying a noun, you always use the subject participles olan and olmayan. Even though the English translation says "rooms that have," Turkish grammar treats the existence of the jacuzzi as a descriptive state, so the object participle (-dık or olduğu) is never used for this specific existential structure.