Sometimes you need to enter a negated operator like ≠. If you’re a C/C++ programmer, you might think that != should map to ≠, since that’s what != means in those languages (and some others). But since in mathematics ! means factorial, this choice is a bad idea for inputting ≠ into mathematical text. You can type in \ne to get ≠, but there’s the simpler combination: /=. In the linear format used in Microsoft Office math, / is used for “stacked” fractions. But /= building up to a fraction with an empty denominator followed by an equal sign isn’t very useful. Also if you really want such a fraction, you can get it by typing /<space>.
Accordingly in Office 2010 math entry, /= builds up to ≠. This approach can be used to input many other negated operators as listed in the following table
Operator
Negated op
Input
<
≮
/<
=
≠
/=
>
≯
/>
∃
∄
/\exists
∈
∉
/\in
∋
∌
/\ni
∼
≁
/\sim
≃
≄
/\simeq
≅
≇
/\cong
≈
≉
/\approx
≍
≭
/\asymp
≡
≢
/\equiv
≤
≰
/\le
≥
≱
/\ge
≶
≸
/\lessgtr
≷
≹
/\gtrless
≽
⋡
/\succeq
≺
⊀
/\prec
≻
⊁
/\succ
≼
⋠
/\preceq
⊂
⊄
/\subset
⊃
⊅
/\supset
⊆
⊈
/\subseteq
⊇
⊉
/\supseteq
⊑
⋢
/\sqsubseteq
⊒
⋣
/\sqsupseteq
All of these operators are in the U+2200 Unicode block (Mathematical Operators) except for the ASCII characters <, =, and >. TeX has a similar, but more verbose approach that uses the control word \not followed by the name of the operator. For example, in TeX, \not\exists produces ∄.
Note that if you don’t like an automatic translation when entering math, you can undo the translation by typing ctrl+z. This way of entering negated operators along with some other extensions to the linear format will be documented in a future version of Unicode Technical Note #28.