Triangle Circles
- Adams' Circle
- Ajima-Malfatti Points
- Anticomplementary Circle
- Apollonian Circle
- Apollonius Circle
- Auxiliary Circle
- Bevan Circle
- Brocard Circle
- Castillon's Problem
- Central Circle
- Cevian Circle
- Circle Function
- Circle Inscribing
- Circumcircle
- Circumradius
- Congruent Incircles
- Congruent Incircles Point
- Conway Circle
- Cosine Circle
- D-Triangle
- de Longchamps Circle
- Dou Circle
- Droz-Farny Circles
- Escribed Circles
- Euler-Gergonne-Soddy Circle
- Excentral Circle
- Excircles
- Excircles Radical Circle
- Extangents Circle
- External Center of Similitude
- Feuerbach Circle
- Feuerbach's Conic Theorem
- Feuerbach's Theorem
- First Brocard Circle
- First Droz-Farny Circle
- First Lemoine Circle
- First Neuberg Circle
- Fontené Theorems
- Fuhrmann Circle
- Gallatly Circle
- GEOS Circle
- Half-Altitude Circle
- Half-Moses Circle
- Hexyl Circle
- Incenter-Excenter Circle
- Incentral Circle
- Incircle
- Inner Napoleon Circle
- Inner Soddy Center
- Inner Soddy Circle
- Inner Vecten Circle
- Inradius
- Intangents Circle
- Internal Center of Similitude
- Johnson-Yff Circles
- Kenmotu Circle
- Lemoine Circles
- Lester Circle
- Longuet-Higgins Circle
- Lucas Central Circle
- Lucas Circles
- Lucas Circles Radical Circle
- Lucas Inner Circle
- Lucas Inner Triangle
- MacBeath Circle
- Malfatti Circles
- Malfatti's Problem
- Malfatti Triangle
- Mandart Circle
- Mannheim Circles
- Marble Problem
- McCay Circles Radical Circle
- Medial Circle
- Mid-Arc Points
- Midpoint Ellipse
- Miquel Circles
- Miquel's Pivot Theorem
- Miquel Point
- Miquel's Theorem
- Mixtilinear Circle
- Mixtilinear Incircles
- Mixtilinear Incircles Radical Circle
- Morley's Circle
- Moses Circle
- Moses-Longuet-Higgins Circle
- Neuberg Circles
- Neuberg Circles Radical Circle
- Orthic Circle
- Orthocentroidal Circle
- Orthoptic Circle of the Steiner Inellipse
- Outer Napoleon Circle
- Outer Soddy Center
- Outer Soddy Circle
- Outer Vecten Circle
- Parry Circle
- Pedal Circle
- Pivot Theorem
- Polar Circle
- Power Circles
- Proportionally-Cutting Circle
- Radical Axis
- Radical Circle
- Radical Line
- Reflection Circle
- Second Brocard Circle
- Second Droz-Farny Circle
- Second Lemoine Circle
- Second Neuberg Circle
- Second Steiner Circle
- Simson Line
- Sine-Triple-Angle Circle
- Six Circles Theorem
- Soddy Circles
- Spieker Circle
- Spieker Radical Circle
- Stammler Circle
- Stammler Circles
- Stammler Circles Radical Circle
- Steiner Circle
- Steiner Deltoid
- Stevanović Circle
- Symmedial Circle
- Tangential Circle
- Tangential Mid-Arc Circle
- Taylor Circle
- Third Lemoine Circle
- Triangle Transformation Principle
- Tucker Circles
- Tucker Hexagon
- van Lamoen Circle
- Yff Central Circle
- Yff Circles
- Yff Contact Circle
- Yiu Circle
- Yiu Circles