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Mathematics LibreTexts

Glossary

  • Page ID
    87143
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    Example and Directions
    Words (or words that have the same definition) The definition is case sensitive (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] (Optional) Caption for Image (Optional) External or Internal Link (Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...") (Eg. "Relating to genes or heredity") The infamous double helix https://bio.libretexts.org/ CC-BY-SA; Delmar Larsen
    Glossary Entries

    Word(s)

    Definition

    Image Caption Link Source
    Antisymmetric A relation R on a

    set

    A is an antisymmetric relation provided that for all x,y∈Ax, if x R y and y R x, then x=y.
           
    Biconditional P if and only if Q        
    Bijection A function f:A -> B such that f is both an injection and a surjection        
    Bipartite graph A graph for which it is possible to divide the vertices into two disjoint sets such that there are no edges between any two vertices in the same

    set

           
    Boolean algebra a lattice that contains a least element and a greatest element and that is both complemented and distributive. The notation [B;∨,∧,¯] is used to denote the boolean algebra with operations join, meet and complementation.        
    Cardinality The number of elements in a set        
    Chromatic number The minimum number of colors required in a proper vertex coloring of the graph        
    Complete graph A graph in which every pair of vertices is adjacent        
    Complement of a set Let U be the universal set. Ac ={x in U, x is not in A}        
    Conditional Statement If P then Q. P is the antecedent (hypothesis) and Q is the consequent (conclusion)        
    Congruent Two integers are congruent mod n (n a positive integer) if the integers leave the same remainder upon division by n        
    Conjecture a guess in mathematics        
    Conjunction P and Q        
    Contrapositive Of the conditional, if not Q then not P, logically equivalent to if P then Q        
    Converse Of the conditional, if Q then P        
    Countably infinite A set that can be put into one-to-one correspondence with the set of natural numbers        
    Cyclic group Group G is cyclic if there exists a∈G such that the cyclic subgroup generated by a, ⟨a⟩ equals all of G. That is, G={na|n∈Z} in which case a is called a generator of G. The reader should note that additive notation is used for G        
    Digraph A directed graph        
    Direct Proof Argument that is based on "If P then Q" and "P" implies Q        
    Disjunction P and Q        
    Division algorithm

    Let m and d be integers with d>0. Then, there exists unique integers q and r with 0<=r < d such that

    m = dq+r

           
    Equivalence class
    For each a∈A, the equivalence class of aa determined by ∼ is the subset of A, denoted by [a], consisting of all the elements of A that are equivalent to a
           
    Equivalence relation A relation that is reflexive, symmetric and transitive        
    Euclidean algorithm

    Let a and b be integers with a≠0 and b>0. Then gcd(a, b) is the only natural number d such that

    (a) d divides a and d divides b, and
    (b) if k is an integer that divides both a and b, then k divides d

           
    Euler circuit An Euler path which starts and stops at the same vertex        
    Euler path A walk which uses each edge exactly once        
    Existential operator There exists        
    Formal Language If A is an alphabet, a formal language over A is a subset of A.        
    Graph an ordered pair G=(V,E) consisting of a nonempty

    set

    V (called the vertices) and a

    set

    E (called the edges) of two-element subsets of V
           
    Greatest common divisor
    The largest natural number that divides both a and b is called the greatest common divisor of a and b
           
    Hasse diagram an illustration of a poset        
    Homomorphism Let [G;∗] and [G′;⋄]be groups. θ:G→G′ is a homomorphism if θ(x∗y)=θ(x)⋄θ(y) for all x,y∈G        
    Indirect Proof Argument based upon the contrapositive        
    Injection A function f:A->B is an injection, if for every a and b in the domain of f, f(a)=f(b) implies a = b.        
    Intersection of two sets Let U be the universal set. A intersect B = {x in U, x is in A and x is in B}        
    Inverse Of the conditional, if not P then not Q        
    Isomorphism
    between two graphs G1 and G2 is a

    bijection

    f:V1→V2 between the vertices of the graphs such that if {a,b} is an edge in G1 then {f(a),f(b)} is an edge in G2
           
    Lattice a poset (L,⪯)for which every pair of elements has a greatest lower bound and least upper bound        
    Logical equivalence Two expressions are logically equivalent provided that they have the same truth value for all possible combinations of truth values for all variables appearing in the two expressions        
    Monoid

    a

    set

    M together with a binary operation ∗∗ with the properties
    • ∗∗ is associative: ∀a,b,c∈M, (a∗b)∗c=a∗(b∗c) and
    • ∗∗ has an identity in M:M: ∃e∈Msuch that ∀a∈M, a∗e=e∗a=a
           
    Negation not P        
    Partial order

    Let ⪯⪯ be a

    relation

    on a

    set

    L.L. We say that ⪯⪯ is a partial ordering on LL if it is

    reflexive

    ,

    antisymmetric

    , and

    transitive

    . That is:
    1. ⪯ is

      reflexive

      : a⪯a∀a∈L
    2. ⪯ is

      antisymmetric

      : a⪯b and a≠b⇒b⋠a∀a,b∈L
    3. ⪯ is

      transitive

      : a⪯b and b⪯c⇒a⪯c∀a,b,c∈L

    The

    set

    together with the

    relation

    (L,⪯) is called a poset.
           
    Principle of Mathematical Induction

    A technique of proof whereby

    If T is a subset of N such that

    1. 1∈T, and
    2. For every k∈N, if k∈T, then (k+1)∈T.

    Then T=N.

           
    Proof by Contradiction Given "If P then Q" assume "P and not Q" to arrive at "P and not P"        
    Reflexive
    The relation R is reflexive on A provided that for each x∈A, x R x or, equivalently, (x,x)∈R
           
    Relation Let A and B be sets. A relation R from the

    set A to the set

    B is a subset of A×B
           
    Set A well-defined collection of objects        
    Statement a declarative sentence that is either true or false but not both        
    String
    A string of length n, n⩾1 over alphabet A is a sequence of nn letters from A: a1a2…an. The set of all strings over A is A*.
           
    Subgraph We say that G1=(V1,E1) is a subgraph of G2=(V2,E2) provided V1⊆V2 and E1⊆E2        
    Surjection A function f:A ->B is a surjection if for every b in B there exists an a in A such that f(a)=b.        
    Symmetric

    The relation R is symmetric provided that for every x,y∈A, if x R y, then y R x or, equivalently, for every x,y∈Ax, if (x,y)∈R, then (y,x)∈R

           
    Symmetric group
    Let A be a nonempty

    set

    . The

    set

    of all permutations on A with the operation of function composition is called the

    symmetric

    group on A, denoted SA.
           
    Tree A (connected) graph with no cycles. (A non-connected graph with no cycles is called a forest.) The vertices in a tree with degree 1 are called leaves        
    The Well-Ordering Principle for the natural numbers states that any nonempty

    set

    of natural numbers must contain a least element

    equivalent to the Principle of Mathematical Induction

           
    Transitive The relation R is transitive provided that for every x,y,z∈A, if x R y and y R z, then x R z or, equivalently, for every x,y,z∈A, if (x,y)∈R and (y,z)∈R, then (x,z)∈R        
    Truth table a summary of all the truth values of a statement        
    Uncountably infinite An infinite set for which there does not exist a one to one correspondence with the natural numbers        
    Union of two sets Let U be the universal set. A U B ={x in U, such that x is in A or x is in B}        
    Universal operator For all or for every        
    Vertex coloring An assignment of colors to each of the vertices of a graph. A vertex coloring is proper if adjacent vertices are always colored differently        
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