A membership organization is a broad term for a group or body which has members. Typically any member of the public can join and a membership fee or "subscription" is payable, but arrangements vary widely. The legal form also varies widely, from very small voluntary associations, which may or may not be formally established, to very large organizations like the National Trust in Britain, which had 3.7 million members in 2010, paying about £50 per year.[1] This, like very many membership organizations, is established as a charity (non profit) though it has commercial subsidiaries.
Types of membership organizations include "Friends of ..." organizations, other support groups, political parties and a wide range of others. Some clubs would typically be covered by the term, but not country clubs and others which exist primarily to use specific facilities.