origin: (1455) "quorum of the Shire" or the justices collectively; Latin qui= "who" or Latin quōrum= whom.
I attended a government meeting over the weekend, and due to delays in traffic caused by an important baseball game, the head of the meeting explained, "We do not currently have enough people for a quorum, so this currently is a town hall gathering" = an informal event. When two latecomers arrived and took their place on stage, the meeting was upgraded back to "quorum".
Naturally I thought, "This would make a good word for 1word1day!"
There is no set number for any group meeting of officials to constitute a quorum, it is set by the members of the body -- without that chosen number of representatives, specific motions, business, and/or decisions cannot be made or considered legally binding. In both houses of Congress, a quorum simply means a majority of members need to be present (though not specifically designated individuals).
In the Mormon faith, a quorum is also considered the class at which priests reside; in example, the early followers of Jesus are referred to as the "Quorum of the Twelve Apostles".