What is the meaning of the word, "community" to you?
no chuuni answers like "they are my clan, my brotherhood of darkness." please
the oxford definition of it is, A group of people living in the same place or having a particular characteristic in common. Does it mean that to you?

How big is a community? does it exclude people? at what point does a small gathering become a Community?

I think it becomes a community when there is something that defines the group and holds them together. Maybe that is geographical coincidence, maybe it's all being a fan of the same anime, or maybe it's a common desire to do good. So under that definition, a community can in fact exclude others. As for how large or small a community can be, I think there is no definite number. But that's just my take on it.

After replying I realized this might belong in personal, not literature. Oops.