Hyperreal Number
Hyperreal numbers are an extension of the Real Numbers to include certain classes of infinite and infinitesimal numbers. A hyperreal number 
is said to be finite Iff 
for some Integer 
. is said to be infinitesimalIff 
for all Integers .
References
Keisler, H. J. ``The Hyperreal Line.'' In Real Numbers, Generalizations of the Reals, and Theories of Continua (Ed. P. Ehrlich). Norwell, MA: Kluwer, 1994.
- Dimensionality Theorem
- Dimension Axiom
- Dimension Invariance Theorem
- Diminished Polyhedron
- Diminished Rhombicosidodecahedron
- Dini Expansion
- Dini's Surface
- Dini's Test
- Dinitz Problem
- Diocles's Cissoid
- Diophantine Equation
- Diophantine Equation--10th Powers
- Diophantine Equation--5th Powers
- Diophantine Equation--6th Powers
- Diophantine Equation--7th Powers
- Diophantine Equation--8th Powers
- Diophantine Equation--9th Powers
- Diophantine Equation--Cubic
- Diophantine Equation--Linear
- Diophantine Equation nth Powers
- Diophantine Equation--Quadratic
- Diophantine Equation--Quartic
- Diophantine Quadruple
- Diophantine Set
- Diophantus Property