What Makes a Community Vibrant?

There are lots of reasons why some communities flourish and others languish. Here are a few things that make a community vibrant.

1. A sense of belonging
2. A sense  of sharing and helping other members of the community
3. A few champions that seed the community and help it grow
4. A set of core members that provide some sense of continuity
5. A common purpose or cause may help as well

There may be a lot of other factors. You are welcome to add the ones I missed.