A downward-pointing arrow symbol representing decreasing values, downward mappings, or vertical delimiters in mathematics.
Examples
Decreasing function notation
f(x) \downarrow \text{ as } x \to \infty
Spin state in quantum mechanics
\psi = \left|\downarrow\right\rangle
Minimum value in set notation
\downarrow S = \min\{x : x \in S\}