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  2. Bijection - Wikipedia

    en.wikipedia.org/wiki/Bijection

    A bijection f with domain X (indicated by f: X → Y in functional notation) also defines a converse relation starting in Y and going to X (by turning the arrows around). The process of "turning the arrows around" for an arbitrary function does not, in general , yield a function, but properties (3) and (4) of a bijection say that this inverse ...

  3. Bijection, injection and surjection - Wikipedia

    en.wikipedia.org/wiki/Bijection,_injection_and...

    In other words, each element of the codomain has a non-empty preimage. Equivalently, a function is surjective if its image is equal to its codomain. A surjective function is a surjection. [1] The formal definition is the following.

  4. Order type - Wikipedia

    en.wikipedia.org/wiki/Order_type

    The set of integers and the set of even integers have the same order type, because the mapping is a bijection that preserves the order. But the set of integers and the set of rational numbers (with the standard ordering) do not have the same order type, because even though the sets are of the same size (they are both countably infinite ), there ...

  5. Relation (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Relation_(mathematics)

    In mathematics, a relation denotes some kind of relationship between two objects in a set, which may or may not hold. [1] As an example, " is less than " is a relation on the set of natural numbers ; it holds, for instance, between the values 1 and 3 (denoted as 1 < 3 ), and likewise between 3 and 4 (denoted as 3 < 4 ), but not between the ...

  6. Back-and-forth method - Wikipedia

    en.wikipedia.org/wiki/Back-and-forth_method

    An isomorphism between linear orders is simply a strictly increasing bijection. This result implies, for example, that there exists a strictly increasing bijection between the set of all rational numbers and the set of all real algebraic numbers. any two countably infinite atomless Boolean algebras are isomorphic to each other.

  7. Bijective numeration - Wikipedia

    en.wikipedia.org/wiki/Bijective_numeration

    Bijective numeration is any numeral system in which every non-negative integer can be represented in exactly one way using a finite string of digits.The name refers to the bijection (i.e. one-to-one correspondence) that exists in this case between the set of non-negative integers and the set of finite strings using a finite set of symbols (the "digits").

  8. Graph isomorphism - Wikipedia

    en.wikipedia.org/wiki/Graph_isomorphism

    Under one definition, an isomorphism is a vertex bijection which is both edge-preserving and label-preserving. [ 3 ] [ 4 ] Under another definition, an isomorphism is an edge-preserving vertex bijection which preserves equivalence classes of labels, i.e., vertices with equivalent (e.g., the same) labels are mapped onto the vertices with ...

  9. Glossary of mathematical jargon - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_mathematical...

    In applied fields the word "tight" is often used with the same meaning. [2] smooth Smoothness is a concept which mathematics has endowed with many meanings, from simple differentiability to infinite differentiability to analyticity, and still others which are more complicated. Each such usage attempts to invoke the physically intuitive notion ...