What is defined as the minimum number of members required to be present at a meeting to validate its proceedings?

The concept being defined in the question is a "quorum." A quorum is the minimum number of members that must be present in order for the proceedings of a meeting to be considered valid and for decisions to be made. This ensures that decisions reflect the will of a sufficient portion of the group, thereby promoting fairness and accountability in the decision-making process.

Having a defined quorum is crucial in organizational settings as it protects against decisions being made when a very small number of members are present, which might not accurately represent the views of the entire group. It can be established in an organization's bylaws or governing documents to suit the requirements of that specific group or assembly.

Other concepts mentioned, such as majority, consensus, and supermajority, relate to decision-making thresholds but do not specifically denote the minimum attendance needed to validate a meeting's activities. A majority refers to more than half of the members present voting in favor, consensus implies general agreement among members, and a supermajority requires a larger percentage than a simple majority for particular types of decisions. Thus, none of these terms replace the fundamental role that a quorum plays in confirming the legitimacy of a meeting's outcomes.