A relational symbol representing inequality or non-equivalence between mathematical expressions or values.
Examples
Basic inequality statement
2 + 2 \neq 5
Set element exclusion
x \in \mathbb{R}, x \neq 0
Algebraic condition
\text{For } a,b \in \mathbb{R}, \text{ if } a^2 = b^2 \text{ then } a \neq -b \text{ implies } a = b