A relational symbol indicating a subset relationship with equality allowed, commonly used in order theory and lattices.
Examples
Partial order relation
A \sqsubseteq B \text{ means A is a subset of B or equal to B}
Domain theory ordering
\bot \sqsubseteq x \sqsubseteq \top
Lattice comparison
x \sqsubseteq y \implies f(x) \sqsubseteq f(y)