Quorum

A quorum is the minimum number of members of a group necessary to constitute the group at a meeting. In a deliberative assembly (a body that uses parliamentary procedure, such as a legislature), a quorum is necessary to conduct the business of that group. In contrast, a plenum is a meeting of the full (or rarely nearly full) body. A body, or a meeting or vote of it, is quorate if a quorum is present (or casts valid votes).

The term quorum is from a Middle English wording of the commission formerly issued to justices of the peace, derived from Latin quorum, "of whom", genitive plural of qui, "who". As a result, quora as plural of quorum is not a grammatically well-formed Latin-language construction. In modern times a quorum might be defined as the minimum number of voters needed for a valid election.

Quorums are often required by traditional handbooks of parliamentary procedure such as Robert's Rules of Order. However, quorums have been criticized by social choice theorists for their pathological behavior, including an absurd result called a no-show paradox, where a proposal may pass because too many members oppose it. This has led many jurisdictions and bodies to replace traditional quorums with quorums of votes in favor, i.e. a requirement that any proposal be supported by a certain share of the entire membership to pass (e.g. 25% of all members).