Quadrifrons is a Latin word, meaning four-fronted or four-faced, particularly:

• Form of triumphal arch
  Triumphal arch
  A triumphal arch is a monumental structure in the shape of an archway with one or more arched passageways, often designed to span a road. In its simplest form a triumphal arch consists of two massive piers connected by an arch, crowned with a flat entablature or attic on which a statue might be...
  
   (e.g., at Glanum
  Glanum
  Glanum was an oppidum, or fortified town, founded by a Celto-Ligurian people called the Salyens in the 6th century B.C.,. It was known for the healing power of its spring. It became a Roman city in Provence until its abandonment in 260 A.D....
  
  , Arch of Janus
  Arch of Janus
  The Arch of Janus is the only quadrifrons triumphal arch preserved in Rome, across a crossroads in the Velabrum-Forum Boarium. It was built in the early 4th century of spolia, possibly in honour of Constantine I or Constantius II. Its current name is probably from the Renaissance or later and is...
  
  , Rutupiae
  Rutupiae
  Richborough Castle contains the ruined remains of a Roman Saxon Shore Fort. It situated in Richborough near Sandwich, Kent.The site has many phases of Roman remains, collectively known as Richborough Fort or Richborough Roman Fort, still visible today and under the care of English Heritage.Rutupiæ ...
  
  ) with four arches (one pair opposite each other, and the second pair opposite each other at right angles) and hence with barrel vault
  Barrel vault
  A barrel vault, also known as a tunnel vault or a wagon vault, is an architectural element formed by the extrusion of a single curve along a given distance. The curves are typically circular in shape, lending a semi-cylindrical appearance to the total design...
  
  ed passageway in the form of a cross.
• Aspect of Janus
  Janus
  -General:*Janus , the two-faced Roman god of gates, doors, doorways, beginnings, and endings*Janus , a moon of Saturn*Janus Patera, a shallow volcanic crater on Io, a moon of Jupiter...
  
  , god.

Quadrifrons is believed to be the fourth face of the God Janus and represents an aspect of the God's attitude and life-cycle.

Quadrifrons represents death and destruction or the end of the life-cycle while Trifrons represents wisdom and Bifrons represents virility thus completing the beginning-to-end cycle that begins with Janus itself.

It is also sometimes used in scientific classification, for example, Eremias

Eremias

Eremias is a genus of wall lizards of the family Lacertidae.-Species:*Eremias acutirostris*Eremias afghanistanica*Eremias andersoni*Eremias argus*Eremias arguta*Eremias aria*Eremias brenchleyi*Eremias buechneri...

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