This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as Kissen (pillow).
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+2311 forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
A lozenge ( LOZ-inj; symbol: ◊), often referred to as a diamond, is a form of rhombus. The definition of lozenge is not strictly fixed, and the word is sometimes used simply as a synonym (from Old French losenge) for rhombus. Most often, though, lozenge refers to a thin rhombus—a rhombus with two acute and two obtuse angles, especially one with acute angles of 45°. The lozenge shape is often used in parquetry (with acute angles that are 360°/n with n being an integer higher than 4, because they can be used to form a set of tiles of the same shape and size, reusable to cover the plane in various geometric patterns as the result of a tiling process called tessellation in mathematics) and as decoration on ceramics, silverware and textiles. It also features in heraldry and playing cards.
Representations
System
Representation (click value to copy)
Nº
8977
UTF-8
E2 8C 91
UTF-16
23 11
UTF-32
00 00 23 11
URL-Quoted
%E2%8C%91
HTML hex reference
⌑
Wrong windows-1252 Mojibake
⌑
alias
Kissen (pillow)
Encoding: GB18030 (hex bytes)
81 36 E9 32
RFC 5137
\u'2311'
Bash and Zsh inside echo -e
\u2311
C and C++
\u2311
C#
\u2311
CSS
\002311
Excel
=UNICHAR(8977)
Go
\u2311
JavaScript
\u2311
Modern JavaScript since ES6
\u{2311}
JSON
\u2311
Java
\u2311
Lua
\u{2311}
Matlab
char(8977)
Perl
"\x{2311}"
PHP
\u{2311}
PostgreSQL
U&'\2311'
PowerShell
`u{2311}
Python
\u2311
Ruby
\u{2311}
Rust
\u{2311}
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