U+21A0 Rightwards Two Headed Arrow
U+21A0 was added in Unicode version 1.1 in 1993. It belongs to the block
This character is a Math Symbol and is commonly used, that is, in no specific script. The character is also known as z notation total surjection and fast cursor right.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+21A0 forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with one other glyph.
The CLDR project calls this character “rightwards two headed arrow” for use in screen reading software.
The Wikipedia has the following information about this codepoint:
In mathematics, a surjective function (also known as surjection, or onto function ) is a function f such that, for every element y of the function's codomain, there exists at least one element x in the function's domain such that f(x) = y. In other words, for a function f : X → Y, the codomain Y is the image of the function's domain X. It is not required that x be unique; the function f may map one or more elements of X to the same element of Y.
The term surjective and the related terms injective and bijective were introduced by Nicolas Bourbaki, a group of mainly French 20th-century mathematicians who, under this pseudonym, wrote a series of books presenting an exposition of modern advanced mathematics, beginning in 1935. The French word sur means over or above, and relates to the fact that the image of the domain of a surjective function completely covers the function's codomain.
Any function induces a surjection by restricting its codomain to the image of its domain. Every surjective function has a right inverse assuming the axiom of choice, and every function with a right inverse is necessarily a surjection. The composition of surjective functions is always surjective. Any function can be decomposed into a surjection and an injection.
Representations
System | Representation |
---|---|
Nº | 8608 |
UTF-8 | E2 86 A0 |
UTF-16 | 21 A0 |
UTF-32 | 00 00 21 A0 |
URL-Quoted | %E2%86%A0 |
HTML hex reference | ↠ |
Wrong windows-1252 Mojibake | ↠|
HTML named entity | ↠ |
HTML named entity | ↠ |
alias | z notation total surjection |
alias | fast cursor right |
LATEX | \twoheadrightarrow |
Related Characters
Confusables
Elsewhere
Complete Record
Property | Value |
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1.1 (1993) | |
RIGHTWARDS TWO HEADED ARROW | |
RIGHT TWO HEADED ARROW | |
Arrows | |
Math Symbol | |
Common | |
Other Neutral | |
Not Reordered | |
none | |
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✘ | |
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✘ | |
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✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
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Any | |
✔ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
0 | |
0 | |
0 | |
✘ | |
None | |
— | |
NA | |
Other | |
— | |
✘ | |
✘ | |
✔ | |
✘ | |
Yes | |
Yes | |
|
|
Yes | |
|
|
Yes | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✔ | |
✘ | |
✘ | |
✘ | |
✘ | |
Other | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
Other | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
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None | |
neutral | |
Not Applicable | |
— | |
No_Joining_Group | |
Non Joining | |
Alphabetic | |
none | |
not a number | |
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R |