• A cheerleading stunt
• The building of community capacity by outsiders, for instance agricultural extension
  Agricultural extension
  Agricultural extension was once known as the application of scientific research and new knowledge to agricultural practices through farmer education...
  
  
• Extension (geology), relating to the pulling apart of the Earth's crust and lithosphere
• Extension (kinesiology)
  Extension (kinesiology)
  In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
  
  , movement of a joint whereby one part of the body is moved away from another
• Extension (metaphysics)
  Extension (metaphysics)
  In metaphysics, extension is, roughly speaking, the property of "taking up space". René Descartes defines extension as the property of existing in more than one dimension. For Descartes, the primary characteristic of matter is extension, just as the primary characteristic of mind is consciousness...
  
  , the property of taking up space
• Extension (predicate logic)
  Extension (predicate logic)
  The extension of a predicatea truth-valued functionis the set of tuples of values that, used as arguments, satisfy the predicate. Such a set of tuples is a relation.For example the statement "d2 is the weekday following d1"...
  
  
• Extension (semantics)
  Extension (semantics)
  In any of several studies that treat the use of signs - for example, in linguistics, logic, mathematics, semantics, and semiotics - the extension of a concept, idea, or sign consists of the things to which it applies, in contrast with its comprehension or intension, which consists very roughly of...
  
  , the set of things to which a property is applied
• Filename extension
  Filename extension
  A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
  
  
• Extensional definition
  Extensional definition
  An extensional definition of a concept or term formulates its meaning by specifying its extension, that is, every object that falls under the definition of the concept or term in question....
  
  , a definition that enumerates every individual a term applies to
• Extension (telephone)
  Extension (telephone)
  An extension telephone is an additional telephone wired to the same telephone line as another. In middle 20th century telephone jargon, the first telephone on a line was a "Main Station" and subsequent ones "Extensions". Such extension phones allow making or receiving calls in different rooms,...
  
  , 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.
  Extension Inc.
  Extension, Inc. is a software development company based in Fort Wayne, Indiana that specializes in health information technology that provides communication software for clinicians....
  
   a company
• Extension locus, the gene locus of Melanocortin 1 receptor
  Melanocortin 1 receptor
  The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor , melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic...
  
  
• Continuing education
  Continuing education
  Continuing education is an all-encompassing term within a broad spectrum of post-secondary learning activities and programs. The term is used mainly in the United States and Canada...
  
  , or extension school, a school for continuing education
• Extension, British Columbia, village near Regional District of Nanaimo, British Columbia, Canada
• Eyelash extensions
  Eyelash extensions
  Like hair extensions, eyelash extensions add length, thickness and fullness to natural eyelashes. Synthetic single fiber polyester thread-like materials are applied to individual eyelashes to create a fuller, longer look.- Materials :...
  
  , material applied to eyelashes
• Hair extensions, strands of hair added to existing hair

Music

• Extension (music)
  Extension (music)
  In music, an extension is a set of musical notes that lie outside the standard range or tessitura.-Staff:A note that lies outside the lines of a musical staff is an extension of the staff. The note will lie on a ledger line. Middle C for example is an extension note on both treble and bass clefs,...
  
  , notes that fit outside the standard range
• Extensions (McCoy Tyner album), 1970
• Extensions (Dave Holland album)
  Extensions (Dave Holland album)
  -Track listing:# "Nemesis" - 11:31# "Processional" - 7:16# "Black Hole" - 10:10# "The Oracle" - 14:32# "101° Fahrenheit " - 4:50# "Color Of Mind" - 10:11...
  
  
• Extension (album)
  Extension (album)
  Extension is the third album by American saxophonist George Braith recorded in 1964 and released on the Blue Note label.-Reception:The Allmusic review by Stephen Thomas Erlewine awarded the album 4½ stars and stated "George Braith turned in his strongest record with Extension...
  
  , an album by American saxophonist George Braith
• Extensions (The Manhattan Transfer album), 1979 album

Computing

• Filename extension
  Filename extension
  A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....
  
  , 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)
    Extension (Mac OS)
    On the Apple Macintosh operating system prior to Mac OS X, extensions were small pieces of code that extended the system's functionality. They were run initially at start-up time, and operated by a variety of mechanisms, including trap patching and other code modifying techniques. Initially an...
    
    , particular type of this software
  • Mozilla extensions for Firefox and other Mozilla projects

Analysis

• Carathéodory's extension theorem
  Carathéodory's extension theorem
  In measure theory, Carathéodory's extension theorem states that any σ-finite measure defined on a given ring R of subsets of a given set Ω can be uniquely extended to the σ-algebra generated by R...
  
  
• Continuous linear extension
• M. Riesz extension theorem
  M. Riesz extension theorem
  The M. Riesz extension theorem is a theorem in mathematics, proved by Marcel Riesz during his study of the problem of moments.-Formulation:Let E be a real vector space, F ⊂ E a vector subspace, and let K ⊂ E be a convex cone.A linear functional ...
  
  
• Krein extension theorem
• Hahn–Banach theorem
  Hahn–Banach theorem
  In mathematics, the Hahn–Banach theorem is a central tool in functional analysis. It allows the extension of bounded linear functionals defined on a subspace of some vector space to the whole space, and it also shows that there are "enough" continuous linear functionals defined on every normed...
  
  

Algebra

• Abelian extension
  Abelian extension
  In abstract algebra, an abelian extension is a Galois extension whose Galois group is abelian. When the Galois group is a cyclic group, we have a cyclic extension. More generally, a Galois extension is called solvable if its Galois group is solvable....
  
  
• Algebraic extension
  Algebraic extension
  In abstract algebra, a field extension L/K is called algebraic if every element of L is algebraic over K, i.e. if every element of L is a root of some non-zero polynomial with coefficients in K. Field extensions that are not algebraic, i.e...
  
  
• Artin–Schreier extension
• Central extension
• Cyclotomic extension—see abelian extension
  Abelian extension
  In abstract algebra, an abelian extension is a Galois extension whose Galois group is abelian. When the Galois group is a cyclic group, we have a cyclic extension. More generally, a Galois extension is called solvable if its Galois group is solvable....
  
  
• Degree of a field extension
  Degree of a field extension
  In mathematics, more specifically field theory, the degree of a field extension is a rough measure of the "size" of the extension. The concept plays an important role in many parts of mathematics, including algebra and number theory — indeed in any area where fields appear prominently.-...
  
  
• Dual basis in a field extension
  Dual basis in a field extension
  In mathematics, the linear algebra concept of dual basis can be applied in the context of a finite extension L/K, by using the field trace. This requires the property that the field trace TrL/K provides a non-degenerate quadratic form over K...
  
  
• Extension of modules
• Extension problem
• Field extension
  Field extension
  In abstract algebra, field extensions are the main object of study in field theory. The general idea is to start with a base field and construct in some manner a larger field which contains the base field and satisfies additional properties...
  
  
• Galois extension
  Galois extension
  In mathematics, a Galois extension is an algebraic field extension E/F satisfying certain conditions ; one also says that the extension is Galois. The significance of being a Galois extension is that the extension has a Galois group and obeys the fundamental theorem of Galois theory.The definition...
  
  
• Group extension
  Group extension
  In mathematics, a group extension is a general means of describing a group in terms of a particular normal subgroup and quotient group. If Q and N are two groups, then G is an extension of Q by N if there is a short exact sequence...
  
  
• Integral extension
• Kernel extension theorem
• Kummer extension
• Normal extension
  Normal extension
  In abstract algebra, an algebraic field extension L/K is said to be normal if L is the splitting field of a family of polynomials in K[X]...
  
  
• Quadratic extension
• Quadratic field extension
• Ring extension
  Ring extension
  In mathematics, more specifically in ring theory, a ring extension or extension ring is a ring R with a subring S. We write R/S and say R is a ring extension of S...
  
  
• Separable extension
  Separable extension
  In modern algebra, an algebraic field extension E\supseteq F is a separable extension if and only if for every \alpha\in E, the minimal polynomial of \alpha over F is a separable polynomial . Otherwise, the extension is called inseparable...
  
  
• Simple extension
  Simple extension
  In mathematics, more specifically in field theory, a simple extension is a field extension which is generated by the adjunction of a single element...
  
  
• Splitting of prime ideals in Galois extensions
  Splitting of prime ideals in Galois extensions
  In mathematics, the interplay between the Galois group G of a Galois extension L of a number field K, and the way the prime ideals P of the ring of integers OK factorise as products of prime ideals of OL, provides one of the richest parts of algebraic number theory...
  
  
• Trivial extension—see field extension
  Field extension
  In abstract algebra, field extensions are the main object of study in field theory. The general idea is to start with a base field and construct in some manner a larger field which contains the base field and satisfies additional properties...
  
  

Logic / Set theory

• Axiom of extensionality
  Axiom of extensionality
  In axiomatic set theory and the branches of logic, mathematics, and computer science that use it, the axiom of extensionality, or axiom of extension, is one of the axioms of Zermelo-Fraenkel set theory.- Formal statement :...
  
  
• Extensible cardinal
• Extension (model theory)
• Extension (predicate logic)
  Extension (predicate logic)
  The extension of a predicatea truth-valued functionis the set of tuples of values that, used as arguments, satisfy the predicate. Such a set of tuples is a relation.For example the statement "d2 is the weekday following d1"...
  
  
• Extensionality
  Extensionality
  In logic, extensionality, or extensional equality refers to principles that judge objects to be equal if they have the same external properties...
  
  

Geometry

• Exterior algebra
  Exterior algebra
  In mathematics, the exterior product or wedge product of vectors is an algebraic construction used in Euclidean geometry to study areas, volumes, and their higher-dimensional analogs...
  
  , Grassmann's theory of extension.
• Extension of a polyhedron
  Extension of a polyhedron
  In mathematics, in particular in the theory of polyhedra and polytopes, an extension of a polyhedron P is a polyhedron Q together with an affine or, more generally, projective map π mapping Q onto P....