Mathematical symbols to copy: operators, comparisons, set theory and calculus. Plus the lookalikes that cause real errors.

The lookalikes that cause errors

Several mathematical symbols have an ASCII neighbour that renders almost identically and means something else. These are the ones worth getting right:

Correct	Common substitute	Why it matters
`×` multiplication sign	`x` letter, `*` asterisk	`x` is a variable; `*` is programming notation
`−` minus sign (U+2212)	`-` hyphen (U+002D)	the hyphen is narrower and does not align with `+`
`÷` division sign	`/` solidus	different conventions, not different glyphs
`≈` almost equal	`~` tilde	`~` means “of the order of” in some fields
`∆` increment (U+2206)	`Δ` Greek capital delta (U+0394)	identical glyph, different character
`π` Greek small pi (U+03C0)	`𝜋` italic pi	fonts and search treat them separately

The ∆ / Δ case is the sharpest: they look the same in every font, and a document that mixes them will not find all its deltas with a single search. Unicode’s own guidance is to use the Greek letter for the letter and the increment sign for the operator.

Operators and comparisons

+ − × ÷ ± ∓
= ≠ ≈ ≡ < > ≤ ≥

≤ and ≥ should be preferred over <= and >= in prose. In code, use whatever the language expects — a ≤ in a source file is a syntax error nearly everywhere.

Set theory

∈ ∉ ⊂ ⊃ ∪ ∩ ∅ ∀ ∃

Note that ∅ (empty set, U+2205) is not Ø (Latin capital O with stroke, U+00D8) and not 0̸. The three are visually close and only the first is the mathematical symbol. Danish and Norwegian text uses the second as a letter.

Calculus and analysis

∑ ∏ ∫ ∂ ∇ ∆ √ ∛ ∞ ∝

These render acceptably in running text but are not a substitute for real mathematical typesetting. ∫ on its own has no limits and no integrand placement; anything with a fraction, a superscript or a limit wants LaTeX or MathML instead.

The rule of thumb: Unicode for a symbol inside a sentence, LaTeX for a formula on its own line.

Degrees, per mille and fractions

Symbol	Name	Note
`°`	degree sign	`25°C` — and see the temperature converter
`‰`	per mille	one thousandth, not one hundredth
`½ ¼ ¾`	vulgar fractions	precomposed; only a few exist

The precomposed fractions cover a handful of values. For anything else — ⅐, 5/8 — the options are the fraction slash ⁄ between ordinary digits, or real typesetting. Mixing ½ with 1/3 in the same document looks inconsistent because it is.

Typing them without this page

Method	`≈`
HTML entity	`≈`
Unicode code point	`U+2248`
macOS	`Option` + `X`
LaTeX	`\approx`
Windows	`Alt` + `247` in some applications

macOS has Option shortcuts for a good number of these — Option+= gives ≠, Option+, gives ≤, Option+V gives √. Windows has no comparable set, which is why Alt codes and lists like this one exist.

Maths symbols