Miscellaneous mathematical symbols
As longtime readers of this blog have probably noticed, I like to poke around in Unicode occasionally. It's an endless system of rabbit holes to explore.
This morning I was looking at the Miscellaneous Mathematical Symbols block. These are mostly obscure symbols, though I'm sure for each symbol that I think is obscure, there is someone out there who uses it routinely.
PerpendicularThe only common symbol in this block is (U+27C2) for perpendicular. Even so, this symbol is a variation on (U+22A5). The distinction is semantic rather than visual: U+22A5 is used for the Boolean value false."
In addition to using to denote perpendicular lines, some (e.g. Donald Knuth) use the symbol to denote that two integers are relatively prime.
Geometric algebraThe block contains (U+27D1) which is used in geometric algebra for the geometric product, a.k.a. the dot-wedge product. The block also contains the symbol for the dual operator (U+27c7), the geometric antiproduct. Incidentally, Eric Lengyel's Projective Geometric Algebra site officially sponsors these two Unicode symbols.
I'm sure these symbols predate Eric Lengyel's use of them, but I can only recall seeing them used in his work.
Database joinsUnicode has four symbols for database joins. The bowtie symbol (U+2A1D) is used for inner (natural) joins is in another block. The Miscellaneous Mathematical Symbols block has three other symbols for outer joins: left, right, and full. I posted a table of these on @CompSciFact this morning.
Angle brackets- Computer Science (@CompSciFact) April 14, 2025
The Miscellaneous Mathematical Symbols block also has angle brackets: (U+27E8) and (U+27E9). These correspond to \langle and \rangle in LaTeX. I've used the LaTeX commands, but I wasn't sure whether I'd ever used the Unicode characters. I searched this blog and found that I did indeed use the characters in my post on the Gram matrix.
More posts on math notationThe post Miscellaneous mathematical symbols first appeared on John D. Cook.