Denumerable Set
A Set is denumerable if a prescription can be given for identifying its members one at a time. Such a set is saidto have Cardinal Number Aleph-0. Examples of denumerable sets include AlgebraicNumbers, Integers, and Rational Numbers. Once onedenumerable set 
is given, any other set which can be put into a One-to-One correspondence with is alsodenumerable. Examples of nondenumerable sets include the Real, Complex,Irrational, and Transcendental Numbers.
References
Courant, R. and Robbins, H. ``The Denumerability of the Rational Number and the Non-Denumerability of the Continuum.'' §2.4.2 in What is Mathematics?: An Elementary Approach to Ideas and Methods, 2nd ed. Oxford, England: Oxford University Press, pp. 79-83, 1996.
- Helly Number
- Helly's Theorem
- Helmholtz Differential Equation
- Helmholtz Differential Equation--Bipolar Coordinates
- Helmholtz Differential Equation--Cartesian Coordinates
- Helmholtz Differential Equation--Circular Cylindrical Coordinates
- Helmholtz Differential Equation--Confocal Ellipsoidal Coordinates
- Helmholtz Differential Equation--Confocal Paraboloidal Coordinates
- Helmholtz Differential Equation--Conical Coordinates
- Helmholtz Differential Equation--Elliptic Cylindrical Coordinates
- Helmholtz Differential Equation--Oblate Spheroidal Coordinates
- Helmholtz Differential Equation--Parabolic Coordinates
- Helmholtz Differential Equation--Parabolic Cylindrical Coordinates
- Helmholtz Differential Equation Polar Coordinates
- Helmholtz Differential Equation--Prolate Spheroidal Coordinates
- Helmholtz Differential Equation--Spherical Coordinates
- Helmholtz Differential Equation--Spherical Surface
- Helmholtz Differential Equation--Toroidal Coordinates
- Helmholtz's Theorem
- Helson-Szegö Measure
- Hemicylindrical Function
- Hemisphere
- Hemispherical Function
- Hempel's Paradox
- Hendecagon