Wikipedia lists several dot characters in Unicode. These are the ones that are ambiguous to me:
- interpunct, middle dot (·)
·
·
U+00B7
"midpoint (in typography)" - dot operator (⋅)
⋅
⋅
U+22C5
- bullet operator (∙)
∙
U+2219
"(mathematics)" - bullet (•)
•
•
U+2022
"black small circle" "often used to mark list items"
I'm mostly interested in the Unicode characters, but Math.SE told me to try here, and LaTeX likewise has:
\cdot
\cdotp
\bullet
\textbullet
For example:
- Wikipedia shows multiplication as both "x ⋅ y" ("dot operator") and "x ∙ y" ("bullet operator") in the same paragraph.
- WP List of mathematical symbols uses "middle dot" for multiplication.
- WP Multiplication article uses
\cdot
for scalar multiplication. - WP says the matrix dot product should be written using the "bullet operator" character, like "a ∙ b".
- The WP Dot product article uses the LaTeX
\cdot
character for dot products. - Wikipedia shows a raised decimal point example "£21·48", which uses the "middle dot" character.
- Wikipedia notates chemistry hydrates like "CuSO4 · 5H2O", which uses the "middle dot" character.
- Combined units can also be written with a dot, like "N·m". Wikipedia uses a "middle dot" for this, not the "dot operator".
- Characters in SI notations has a paragraph on combined units, seeming to say that dot operator is preferred for this, like "N⋅m".
- Wolfram Alpha considers
\cdot
and·
to be equivalent, as well as\bullet
and•
. Valid?
Of course it's pedantic, they all look the same, and the meaning can always be assumed from context, but I'd like to know, once and for all, which Unicode/HTML and LaTeX characters are semantically correct in each application?
(If there are other examples I left out, feel free to edit the question and add them.)