Mapping of important parts of the Universal Character Set (usually referred to as Unicode) for English Wikipedia.
The table
editScript error: No such module "UCS".
Arithmetic
editAddition: “+”.
Subtraction and opposite/negative: “−” (−) in text, “-” in arguments of templates.
Multiplication: “×” (×), “⋅” (⋅); no substitutes shall be used.
Division: “/” (usually), “ ⁄ ” (virtually unused), “ ∕ ” (sometimes).
Specific symbols
editAsterisk
editNot a multiplication sign (except in source code in some languages).
Hyphen-minus
editDual use: as a hyphen in the text and minus sign in certain wiki contexts.
Slash
editDual use: as a punctuation and as a #division sign.
Degree sign
edit“°” is a separate character! Shall never be substituted with “0” or “o” in superscript!
Dashes
editSeveral flavours of, but – is the preferred.
Quotation marks
editAll but “ " ” and “ ' ” are frowned upon. Also, “ ’ ” is sometimes mistakenly used as a substitute for prime (′) and vice versa.
Junk characters
editStandalone “accents”
editBoth “ ´ ” and “ ` ” are virtually useless without the overstrike feature, but are sometimes mistakenly used instead of quotation marks. Though, “`” is an ASCII character and is actually used in some scripting languages.
Superscripts and fractions
editUnicode superscripts and precomposed fractions are generally discouraged. Though, they may be used in edit summaries where text formatting is unavailable.
Ordinal indicators
edit“º” and “ª” are useless is English language, but the former is sometimes mistakenly used as a substitute for #Degree sign.
Arrows
editLeft, right, and left–right arrows are very common in Wikipedia. The “⇌” symbols is used for reactions, but is rendered as image instead of the character: see {{eqm}}.