U+21D4 Left Right Double Arrow
U+21D4 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 glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. If its East Asian Width is “narrow”, U+21D4 forms a word with similar characters, which prevents a line break inside it. Otherwise it allows line breaks around it, except in some numeric contexts.
The CLDR project calls this character “left right double arrow” for use in screen reading software.
The Wikipedia has the following information about this codepoint:
In logic and related fields such as mathematics and philosophy, "if and only if" (often shortened as "iff") is paraphrased by the biconditional, a logical connective between statements. The biconditional is true in two cases, where either both statements are true or both are false. The connective is biconditional (a statement of material equivalence), and can be likened to the standard material conditional ("only if", equal to "if ... then") combined with its reverse ("if"); hence the name. The result is that the truth of either one of the connected statements requires the truth of the other (i.e. either both statements are true, or both are false), though it is controversial whether the connective thus defined is properly rendered by the English "if and only if"—with its pre-existing meaning. For example, P if and only if Q means that P is true whenever Q is true, and the only case in which P is true is if Q is also true, whereas in the case of P if Q, there could be other scenarios where P is true and Q is false.
In writing, phrases commonly used as alternatives to P "if and only if" Q include: Q is necessary and sufficient for P, for P it is necessary and sufficient that Q, P is equivalent (or materially equivalent) to Q (compare with material implication), P precisely if Q, P precisely (or exactly) when Q, P exactly in case Q, and P just in case Q. Some authors regard "iff" as unsuitable in formal writing; others consider it a "borderline case" and tolerate its use. In logical formulae, logical symbols, such as and , are used instead of these phrases; see § Notation below.
Representations
System | Representation |
---|---|
Nº | 8660 |
UTF-8 | E2 87 94 |
UTF-16 | 21 D4 |
UTF-32 | 00 00 21 D4 |
URL-Quoted | %E2%87%94 |
HTML hex reference | ⇔ |
Wrong windows-1252 Mojibake | ⇔ |
HTML named entity | ⇔ |
HTML named entity | ⇔ |
HTML named entity | ⇔ |
HTML named entity | ⇔ |
Encoding: EUC-KR (hex bytes) | A2 A2 |
Encoding: JIS0208 (hex bytes) | A2 CE |
LATEX | \Leftrightarrow |
Adobe Glyph List | arrowdblboth |
Adobe Glyph List | dblarrowleft |
digraph | == |
Related Characters
Elsewhere
Complete Record
Property | Value |
---|---|
1.1 (1993) | |
LEFT RIGHT DOUBLE ARROW | |
— | |
Arrows | |
Math Symbol | |
Common | |
Other Neutral | |
Not Reordered | |
none | |
|
|
✘ | |
|
|
|
|
✘ | |
|
|
|
|
|
|
|
|
|
|
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
|
|
Any | |
✔ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
0 | |
0 | |
0 | |
✘ | |
None | |
— | |
NA | |
Other | |
— | |
✘ | |
✘ | |
✔ | |
✘ | |
Yes | |
Yes | |
|
|
Yes | |
|
|
Yes | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✔ | |
✘ | |
✘ | |
✘ | |
✘ | |
Other | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
Other | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
✘ | |
|
|
None | |
ambiguous | |
Not Applicable | |
— | |
No_Joining_Group | |
Non Joining | |
Ambiguous (Alphabetic or Ideographic) | |
none | |
not a number | |
|
|
R |