orientation preserving mappingorientation reversingorientation reversing mappingorientedoriented atlasoriented curveoriented manifoldoriented planeoriented simplexoriented surfaceoriented tangent lineorientingorificeoriginorigin of a rayorigin of a referenceorigin of cartesian coordinatesorigin of coordinatesorigin of vectororigin orthocenteroriginaloriginal assumptionoriginal axiomoriginal diagramoriginal matrixoriginal observationsoriginal scoresoriginal setoriginal statementoriginal treeoriginallyorthic triangleortho complementorthocenterorthodromieorthogonalorthogonal affinityorthogonal axonometryorthogonal basisorthogonal circlesorthogonal complementorthogonal complement grouporthogonal complement group projectionorthogonal componentorthogonal contactsorthogonal coordinate systemorthogonal coordinatesorthogonal curvesorthogonal curvilinear coordiantesorthogonal curvilinear coordinates
