This definition was sent in by Mary D.:
Community, like the definition of “church,” often implies a physical place but really it means people. Something ties them together, but it is not necessarily spatial. It may be common beliefs, interests, or even shared problems; something that connects people intellectually, emotionally, and/or spiritually. In addition, the ties that bring them together are strong enough that the members of the community will help other member(s) if someone is in need. This gives members a feeling of comfort, safety and stability, and also gives them a sense of ownership to the group–something to keep them invested it, if you will.
I’ve seen people find their “community” through obvious connections such as neighborhood, school, work, or church, but also AA, off-roading or roller derby clubs. Online communities can even be strong–I blogged anonymously about my eating disorder for a while and formed some pretty strong bonds with other girls (and one dude blogging about his wife) that way. It was really a lifeline during the dark days.
I think I’d argue that communities bound by shared beliefs or struggles tend to be stronger than those forged by hobbies, place, or profession. At least if you are using the definition that part of a community is the helping each other out aspect.