Extension

Extension may refer to:

• A cheerleading stunt
• The building of community capacity by outsiders, for instance agricultural extension
• Extension (geology), relating to the pulling apart of the Earth's crust and lithosphere
• Extension (kinesiology), movement of a joint whereby one part of the body is moved away from another
• Extension (metaphysics), the property of taking up space
• Extension (predicate logic)
• Extension Inc., a healthcare information technology company that focuses on hospital communication
• Extension (semantics), the set of things to which a property is applied
• Filename extension
• Extensional definition, a definition that enumerates every individual a term applies to
• Extension (telephone), telephone line attached to a main line or to a PBX or Centrex system
• Extension cable
• Extentually, The act of going beyond one's regular limit
• Extension Inc. a company
• Extension locus, the gene locus of Melanocortin 1 receptor
• Continuing education, or extension school, a school for continuing education
• Extension, British Columbia, village near Regional District of Nanaimo, British Columbia, Canada
• Eyelash extensions, material applied to eyelashes
• Hair extensions, strands of hair added to existing hair

Music

• Extension (music), notes that fit outside the standard range
• Extensions (McCoy Tyner album), 1970
• Extensions (Dave Holland album)
• Extension (album), an album by American saxophonist George Braith
• Extensions (The Manhattan Transfer album), 1979 album

Computing

• Filename extension, suffix to the name of a computer file, designed to show its format
• Software extension, a file containing programming that serves to extend the capabilities of or data available to a more basic program
  • Extension (Mac OS), particular type of this software
  • Mozilla extensions for Firefox and other Mozilla projects

Mathematics

In mathematics, the word "extension" has many uses. See:

Analysis

• Carathéodory's extension theorem
• Continuous linear extension
• M. Riesz extension theorem
• Krein extension theorem
• Hahn–Banach theorem

Algebra

• Abelian extension
• Algebraic extension
• Artin–Schreier extension
• Central extension
• Cyclotomic extension—see abelian extension
• Degree of a field extension
• Dual basis in a field extension
• Extension of modules
• Extension problem
• Field extension
• Galois extension
• Group extension
• Integral extension
• Kernel extension theorem
• Kummer extension
• Normal extension
• Quadratic extension
• Quadratic field extension
• Ring extension
• Separable extension
• Simple extension
• Splitting of prime ideals in Galois extensions
• Trivial extension—see field extension

Algebraic geometry

• Sheaf extension

Logic / Set theory

• Axiom of extensionality
• Extensible cardinal
• Extension (model theory)
• Extension (predicate logic)
• Extensionality

Order theory

• Linear extension

Probability theory

• Kolmogorov extension theorem

Topology

• Homotopy extension property
• Tietze extension theorem

Geometry

• Exterior algebra, Grassmann's theory of extension.
• Extension of a polyhedron