Category
page 1Homotopy theory

Dennis Sullivan
American mathematician

homotopy
thumb|The two dashed Path (topology)|paths shown above are homotopic relative to their endpoints. The animation represents one possible homotopy.
In topology, two continuous functions from one topological space to another are called homotopic (from and ) if one can be "continuously deformed" into the other, such a deformation being called a homotopy ( ; ) between the two functions. A notable use of homotopy is the definition of homotopy groups and cohomotopy groups, important invariants in algebraic topology.
fundamental group
mathematical group of the homotopy classes of loops in a topological space
Frank Adams
British mathematician (1930–1989)
covering space
type of continuous map in topology
contractible space
Can be continuously shrunk to a point
CW complex
type of topological space
groupoid
path
in topology, a continuous function between two points
homotopy group
algebraic construct classifying topological spaces

monodromy
thumb|The imaginary part of the complex logarithm. Trying to define the complex logarithm on \C-\{0\} gives different answers along different paths. This leads to an infinite cyclic monodromy group and a covering of \C-\{0\} by a [[helicoid (an example of a Riemann surface).]]
Seifert–van Kampen theorem
a theorem in topology describing the fundamental group of a space in terms of a cover of the space by two open path-connected subspaces
Hopf fibration
fiber bundle of the 3-sphere over the 2-sphere, with 1-spheres as fibers
homotopy theory
subfield of algebraic topology dealing with structures invariant under homotopy equivalence
wedge sum
"one-point union" of a family of topological spaces
suspension
quotient space; operation of suspension creates a way of moving up in dimension (dimension n + 1)

section
right inverse of a fiber bundle map
loop space
space of basepoint preserving maps from a circle
pointed space
topological space with a distinguished point
simplicial set
construction in categorical homotopy theory; contravariant functor from the simplex category to the category of sets
compactly generated space
topological space
simplex category
small category, whose objects are sets of natural numbers of the form {0,1,…,n}, and whose morphisms are nondecreasing functions
line bundle
one-dimensional vector bundle
cofibration
In mathematics, in particular homotopy theory, a continuous mapping between topological spaces
homotopy type theory
variant of type theory incorporating the univalence axiom of Voevodsky
homotopy lifting property
homotopy theory in algebraic topology
Eilenberg–MacLane space
topological space with homotopy concentrated in a single degree
smash product
binary operation between two pointed spaces: X ⨳ Y = (X × Y) / X ∨ Y
quasi-category
In mathematics, more specifically category theory, a quasi-category (also called quasicategory, weak Kan complex, inner Kan complex, infinity category, ∞-category, Boardman complex, quategory) is a generalization of the notion of a category. The study of such generalizations is known as higher category theory.
semi-locally simply connected space
Property in algebraic topology
H-space
In mathematics, an H-space is a homotopy-theoretic version of a generalization of the notion of topological group, in which the axioms on associativity and inverses are removed.
model category
mathematical category with weak equivalences, fibrations and cofibrations
obstruction theory
Mathematical theories
classifying space
topological space equipped with a principal bundle with the property that any principal bundle (with the same fiber group) over a paracompact manifold is isomorphic to a pullback of the principal bundle over this topological space
Postnikov system
in mathematics, a topological construction
N-connected
Hopf invariant
Homotopy invariant of maps between spheres
homotopy extension property
property in algebraic topology
Aspherical space
concept in topology
homotopy group of a sphere
how spheres of various dimensions can wrap around each other
Puppe sequence
construction in algebraic topology that constructs a long (co)exact sequence from a (co)fibration
stable homotopy theory
the study of spectra