This character is a Math Symbol and is commonly used, that is, in no specific script. The character is also known as composite function and APL jot.
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+2218 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 “ring operator” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: composition, operator, ring.
The Wikipedia has the following information about this codepoint:
In mathematics, the composition operator takes two functions, and , and returns a new function . Thus, the function g is applied after applying f to x.
Reverse composition, sometimes denoted , applies the operation in the opposite order, applying first and second. Intuitively, reverse composition is a chaining process in which the output of function f feeds the input of function g.
The composition of functions is a special case of the composition of relations, sometimes also denoted by . As a result, all properties of composition of relations are true of composition of functions, such as associativity.
Representations
System
Representation (click value to copy)
Nº
8728
UTF-8
E2 88 98
UTF-16
22 18
UTF-32
00 00 22 18
URL-Quoted
%E2%88%98
HTML hex reference
∘
Wrong windows-1252 Mojibake
∘
HTML named entity
∘
HTML named entity
∘
alias
composite function
alias
APL jot
Encoding: GB18030 (hex bytes)
81 36 D3 36
LATEX
\circ
digraph
Ob
RFC 5137
\u'2218'
Bash and Zsh inside echo -e
\u2218
C and C++
\u2218
C#
\u2218
CSS
\002218
Excel
=UNICHAR(8728)
Go
\u2218
JavaScript
\u2218
Modern JavaScript since ES6
\u{2218}
JSON
\u2218
Java
\u2218
Lua
\u{2218}
Matlab
char(8728)
Perl
"\x{2218}"
PHP
\u{2218}
PostgreSQL
U&'\2218'
PowerShell
`u{2218}
Python
\u2218
Ruby
\u{2218}
Rust
\u{2218}
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