What is community?

Community — the word is bandied about in digital channels like sauce at a BBQ picnic. But what is it really? Here are five traits I think are necessary for me to feel like I’m part of a community:

  1. Members know me  and I know them — with varying degrees of familiarity.
  2. There is a sense of mutual purpose.
  3. There are clear and articulated ways for members to engage.
  4. There are sustained communications that are both centrally-driven and distributed amongst the membership itself.
  5. There is a sense of mutual identity.

What am I missing? How do you create community for your donors?