* The Sun is a star. Stars belong to galaxies.

* Our Sun belongs to the Milky Way galaxy. So, it does belong to a galaxy.

Therefore, the question is asking what our Sun doesn't belong to, implying it might belong to something else.

However, the Sun is a single star. It's not part of a star cluster (a group of stars) or a binary system (two stars orbiting each other).

So, the answer is that our Sun doesn't belong to a star cluster or a binary system.