Linked from
The 11 pages that link to Quorum, each with the reason it gives.
Majority ruleRelated: A majority decision may be valid only if enough members participate.
Board of directorsRelated: A board generally needs a quorum before it can take official action.
LegislatureRelated: A legislature generally needs a quorum before it can make valid decisions.
OstracismRelated: A minimum turnout was required for the result to take effect.
Proxy votingRelated: Proxy participation can help a shareholder meeting reach its quorum.
MinyanNarrower topic: A minyan is a religiously defined quorum with a fixed traditional threshold.
LegislatorRelated: A legislature may be unable to act when too few legislators are present.