In the context of the English constitution and feudal hierarchy, a Peer (or Peer of the Realm) is a person who holds one of the five degrees of nobility: Duke, Marquess, Earl, Viscount, or Baron. The concept originates from the principle of 'pares'—equals—denoting those of sufficient status to provide counsel to the Sovereign and to be judged only by those of equivalent rank. This legal status granted specific privileges, most notably the right to a seat in the High Court of Parliament and immunity from arrest in civil causes.
Historically, peerage was intrinsically linked to land tenure 'in chief' from the Crown, though it transitioned into a personal dignity created by letters patent or writ of summons. From a heraldic perspective, peers are distinguished by specific insignias, including unique coronets of rank, the use of supporters in their achievement of arms, and the right to use the helm of a peer. While the peerage was once the primary legislative body of the kingdom, the House of Lords Reform Act 1999 significantly altered the hereditary nature of its political function.