Ray
A Vector 
from a point 
to a point 
. In Geometry, a ray is usually taken as ahalf-infinite Line with one of the two points and taken to be at Infinity.
- Quasiperfect Number
- Quasiperiodic Function
- Quasiperiodic Motion
- Quasirandom Sequence
- Quasiregular Polyhedron
- Quasirhombicosidodecahedron
- Quasirhombicuboctahedron
- Quasisimple Group
- Quasithin Theorem
- Quasitruncated Cuboctahedron
- Quasitruncated Dodecadocahedron
- Quasitruncated Dodecahedron
- Quasitruncated Great Stellated Dodecahedron
- Quasitruncated Hexahedron
- Quasitruncated Small Stellated Dodecahedron
- Quasi-Unipotent Group
- Quasi-Unipotent Problem
- Quaternary
- Quaternary Tree
- Quaternion
- Quattuordecillion
- Queens Problem
- Queue
- Queuing Theory
- Quicksort