This character is a Other Symbol and is commonly used, that is, in no specific script.
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+21A8 forms with similar adjacent characters prevents a line break inside it.
The CLDR project calls this character “up down arrow with base” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: arrow, base, down, up, with.
The Wikipedia has the following information about this codepoint:
Vertical is a geometric term of location which may refer to:
Vertical direction, the direction aligned with the direction of the force of gravity, up or down
Vertical (angles), a pair of angles opposite each other, formed by two intersecting straight lines that form an "X"
Vertical (music), a musical interval where the two notes sound simultaneously
"Vertical", a type of wine tasting in which different vintages of the same wine type from the same winery are tasted
Vertical Aerospace, stylised as "Vertical", British aerospace manufacturer
Vertical kilometer, a discipline of skyrunning
Vertical market, a market in which vendors offer goods and services specific to an industry
Vertical integration, a management term describing a style of ownership and control
Representations
System
Representation (click value to copy)
Nº
8616
UTF-8
E2 86 A8
UTF-16
21 A8
UTF-32
00 00 21 A8
URL-Quoted
%E2%86%A8
HTML hex reference
↨
Wrong windows-1252 Mojibake
↨
Encoding: GB18030 (hex bytes)
81 36 C8 38
AGL: Latin-5
arrowupdnbse
Adobe Glyph List
arrowupdnbse
Adobe Glyph List
arrowupdownbase
RFC 5137
\u'21A8'
Bash and Zsh inside echo -e
\u21A8
C and C++
\u21A8
C#
\u21A8
CSS
\0021A8
Excel
=UNICHAR(8616)
Go
\u21A8
JavaScript
\u21A8
Modern JavaScript since ES6
\u{21a8}
JSON
\u21A8
Java
\u21A8
Lua
\u{21A8}
Matlab
char(8616)
Perl
"\x{21A8}"
PHP
\u{21a8}
PostgreSQL
U&'\21A8'
PowerShell
`u{21A8}
Python
\u21A8
Ruby
\u{21a8}
Rust
\u{21a8}
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