- operation
- operational
- operative
- operator
- octagonal
- order
- ordinate
- orthocentre
- orthocentric
- osculation
- osculatory
- orthogonal
- orthogonality
- oscular
- osculate
- parabolic
- paraboloid
- paradox
- parallelogram
- parametric
- parallelepiped
- partial correlation
- pencil
- pentahedral
- pentahedron
- period
- permutation
- pi
- place
- plane
- plane geometry
- plus
- point
- polar
- polyhedric
- positive
- postulate
- polygon
- polygonal
- polyhedral
- power
- prime
- probability
- produce
- primitive
- prismoid
- product
- progression
- project
- projective
- prolate
- proportion
- proportional
- projection
- proper
- proportionable
- proposition
- propositional
- prove
- proven
- pseudosphere
- pythagorean
- quadrant
- quadrate
- quadrature
- quantity
- quadric
- quartic
- pyramid
- quadratic
- quaternion
- quintic
- quotient
- radial
- radian
- radical
- radius
- ratio
- rational
- rationalization
- re-entrant
- rationality
- ray
- rationalize
- ready reckoner
- reciprocal
- reciprocation
- rectifiable
- ready-reckone
- real number
- reciprocate
- reciprocity
- rectification
- rectilineal
- rectilinear
- recurrence
- recursive
- reduce
- rectify
- rectilinearity