This character is a Math 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+229E forms with similar adjacent characters prevents a line break inside it.
The CLDR project calls this character “squared plus” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: addition-like, mathematics, plus, squared.
The Wikipedia has the following information about this codepoint:
The Unicode Standard encodes almost all standard characters used in mathematics.
Unicode Technical Report #25 provides comprehensive information about the character repertoire, their properties, and guidelines for implementation.
Mathematical operators and symbols are in multiple Unicode blocks. Some of these blocks are dedicated to, or primarily contain, mathematical characters while others are a mix of mathematical and non-mathematical characters. This article covers all Unicode characters with a derived property of "Math".
Representations
System
Representation (click value to copy)
Nº
8862
UTF-8
E2 8A 9E
UTF-16
22 9E
UTF-32
00 00 22 9E
URL-Quoted
%E2%8A%9E
HTML hex reference
⊞
Wrong windows-1252 Mojibake
⊞
HTML named entity
⊞
HTML named entity
⊞
Encoding: GB18030 (hex bytes)
81 36 DD 39
LATEX
\boxplus
RFC 5137
\u'229E'
Bash and Zsh inside echo -e
\u229E
C and C++
\u229E
C#
\u229E
CSS
\00229E
Excel
=UNICHAR(8862)
Go
\u229E
JavaScript
\u229E
Modern JavaScript since ES6
\u{229e}
JSON
\u229E
Java
\u229E
Lua
\u{229E}
Matlab
char(8862)
Perl
"\x{229E}"
PHP
\u{229e}
PostgreSQL
U&'\229E'
PowerShell
`u{229E}
Python
\u229E
Ruby
\u{229e}
Rust
\u{229e}
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