A relational symbol representing positive or friendly relations, commonly used in abstract algebra and order theory.
Examples
Relation notation in set theory
a \smile b \text{ denotes that }a\text{ is related to }b
Wedge product relation in differential geometry
\alpha \smile \beta = (-1)^{pq}\beta \smile \alpha
Cup product in algebraic topology
H^p(X) \otimes H^q(X) \xrightarrow{\smile} H^{p+q}(X)