Extension

Extension, extend or extended may refer to:

Logic or set theory

 * Axiom of extensionality
 * Extensible cardinal
 * Extension (model theory)
 * Extension (predicate logic), the set of tuples of values that satisfy the predicate
 * Extension (semantics), the set of things to which a property applies
 * Extension by definitions
 * Extensional definition, a definition that enumerates every individual a term applies to
 * Extensionality

Other uses

 * Extension of a function, defined on a larger domain
 * Extension of a polyhedron, in geometry
 * Exterior algebra, Grassmann's theory of extension, in geometry
 * Field extension, in Galois theory
 * Group extension, in abstract algebra and homological algebra
 * Homotopy extension property, in topology
 * Kolmogorov extension theorem, in probability theory
 * Linear extension, in order theory
 * Sheaf extension, in algebraic geometry
 * Tietze extension theorem, in topology
 * Whitney extension theorem, in differential geometry

Music

 * Extension (music), notes that fit outside the standard range
 * Extended (Solar Fields album), 2005
 * Extension (George Braith album), 1964
 * Extension (Clare Fischer album), 1963
 * Extensions (Ahmad Jamal album), 1965
 * Extensions, a 1969 album by Mystic Moods Orchestra
 * Extensions (McCoy Tyner album), 1970
 * Extensions (Dave Holland album), 1988
 * Extensions (The Manhattan Transfer album), 1979
 * Extension (The Extended Mixes), 2023 album reissue by Kylie Minogue

Places

 * Extension, British Columbia, a village near Regional District of Nanaimo, British Columbia, Canada
 * Extension, Louisiana, unincorporated community, United States

Science

 * Extension (geology), relating to the pulling apart of the Earth's crust and lithosphere
 * Extension (anatomy), a movement at a joint that increases the angle between the two ends of the joint; the opposite of flexion
 * Extension locus, the gene locus of Melanocortin 1 receptor

Other uses

 * Agricultural Extension
 * Browser extension, a small software module for customizing a web browser
 * Building extension
 * Continuing education, or extension school, a school for continuing education
 * Cooperative State Research, Education, and Extension Service, a former division of the U.S. Department of Agriculture
 * Extension (metaphysics), the property of stretching out or taking up space
 * Extension (telephone), telephone line attached to a main line or to a PBX or Centrex system
 * Extension cord, power cable with a plug on one end and one or more sockets on the other end
 * Eyelash extensions, material applied to eyelashes
 * Hair extensions, strands of hair added to existing hair
 * Extension, the building of community capacity by outsiders, for instance agricultural extension
 * Filename extension, for computer file systems