Category
page 1Combinatorics on words
formal language
set of strings of symbols that may be constrained by rules that are specific to it; words whose letters are taken from an alphabet and are well-formed according to a specific set of rules
string
data type representing a finite sequence of encoded characters
alphabet
non-empty set of symbols or letters that make up strings in a formal language
presentation of a group
specification of a mathematical group by generators and relaions

superpermutation
thumb|The distribution of permutations in a 3-symbol superpermutation
In combinatorial mathematics, a superpermutation on n symbols is a string that contains each permutation of n symbols as a substring. While trivial superpermutations can simply be made up of every permutation concatenated together, superpermutations can also be shorter (except for the trivial case of n = 1) because overlap is allowed. For instance, in the case of n = 2, the superpermutation 1221 contains all possible permutations (12 and 21), but the shorter string 121 also contains both permutations.
Beatty sequence
a sequence of integers formed by rounding down the integer multiples of a positive irrational number
free object
a “generic” algebraic structure over the given set, fulfilling no other equations except those given by the defining axioms
hyperbolic group
Mathematical concept
ping-pong lemma
theorem about sufficient conditions for ensuring that that several elements in a group acting on a set freely generate a free subgroup of that group
necklace
an equivalence class of n-character strings over an alphabet of size k, taking all rotations as equivalent
free monoid
concept in mathematics
Witt vector
Mathematical concept named for Ernst Witt

HNN extension
basic construction of combinatorial group theory
Lyndon word
String that is strictly smaller in lexicographic order than all of its rotations
Thue number
graph invariant
symbolic dynamics
subfield in mathematics
word
written product of elements of a mathematical group and their inverses
word metric
way to measure distance between any two elements of group (in group theory)
word problem for groups
given a finitely generated group, the algorithmic problem of deciding whether two words in the generators represent the same element
local language
in mathematics, some kind of formal language
squarefree word
a sequence of symbols that does not contain any repeated contiguous subsequence