Half-space may refer to:
*
Half-space (geometry), either of the two parts into which a plane divides Euclidean space
*
Half-space (punctuation), a spacing character half the width of a regular space
* (Poincaré)
Half-space model, a model of 3-dimensional hyperbolic geometry or higher-dimensional hyperbolic geometry using a Euclidean half-space
*
Half-space model (oceanography), an estimate for seabed height in areas without significant subduction
*
Siegel upper half-space
In mathematics, the Siegel upper half-space of degree ''g'' (or genus ''g'') (also called the Siegel upper half-plane) is the set of ''g'' × ''g'' symmetric matrices over the complex numbers whose imaginary part is positive definite. It ...
, a set of complex matrices with positive definite imaginary part
{{disambig