the minimum number of members of a body that must be assembled for proceedings to be constitutionally valid
Mr. Muggeridge offered to fight the committee all round (four being a quorum) — George Augustus Sala
[Middle English, referring to certain usu eminent justices of the peace without whom the bench was not properly constituted, from Latin quorum of whom, genitive pl of qui who; from the wording of the commission formerly issued to justices of the peace]