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A function [d] A relation that is functional and total. For example, the red and green relations in the diagram are functions, but the blue and black ones are not. An injection [d] A function that is injective. For example, the green relation in the diagram is an injection, but the red, blue and black ones are not. A surjection [d]
This set-theoretic definition is based on the fact that a function establishes a relation between the ... of all sets is a class. ... "12. Functions" (PDF).
Formally, given a set and an equivalence relation on , the equivalence class of an element in is denoted [] or, equivalently, [] to emphasize its equivalence relation . The definition of equivalence relations implies that the equivalence classes form a partition of S , {\displaystyle S,} meaning, that every element of the set belongs to exactly ...
The equivalence relations on any set X, when ordered by set inclusion, form a complete lattice, called Con X by convention. The canonical map ker : X^X → Con X, relates the monoid X^X of all functions on X and Con X. ker is surjective but not injective. Less formally, the equivalence relation ker on X, takes each function f : X → X to its ...
This article lists mathematical properties and laws of sets, involving the set-theoretic operations of union, intersection, and complementation and the relations of set equality and set inclusion. It also provides systematic procedures for evaluating expressions, and performing calculations, involving these operations and relations.
For elements a and b of S, Green's relations L, R and J are defined by . a L b if and only if S 1 a = S 1 b.; a R b if and only if a S 1 = b S 1.; a J b if and only if S 1 a S 1 = S 1 b S 1.; That is, a and b are L-related if they generate the same left ideal; R-related if they generate the same right ideal; and J-related if they generate the same two-sided ideal.
In mathematics, the category Rel has the class of sets as objects and binary relations as morphisms. A morphism (or arrow) R : A → B in this category is a relation between the sets A and B, so R ⊆ A × B. The composition of two relations R: A → B and S: B → C is given by (a, c) ∈ S o R ⇔ for some b ∈ B, (a, b) ∈ R and (b, c) ∈ ...
Functions that have inverse functions are said to be invertible. A function is invertible if and only if it is a bijection. Stated in concise mathematical notation, a function f: X → Y is bijective if and only if it satisfies the condition for every y in Y there is a unique x in X with y = f(x).