Affinity groups may have either open or closed membership, although the latter is far more common.

The membership structure is based on open membership with annual dues.

In 1957, open membership was no longer permitted.

The vast majority of Hollins organizations have open membership.

Social enterprise is characterized by open membership and goals widely considered to be in the community or public interest.

The band has a policy of open, collective membership, leading to numerous lineups over the years.

The sorority had "open membership as a fundamental principle"

Some have membership restricted to particular groups, but the majority have open membership.

It has open membership and also provides a certification and directory for animal behaviorists.

The organization has an open membership, which allowed any U.S. voter to draft and support his or her candidate of choice.