\bigtriangledownThe symbol \bigtriangledown is used to represent the nabla or del operator, which is a vector differential operator commonly used in vector calculus. It is used to denote operations such as gradient, divergence, and curl.
Divergence of a vector field \mathbf{F}
\bigtriangledown \cdot \mathbf{F}Curl of a vector field \mathbf{F}
\bigtriangledown \times \mathbf{F}Gradient of a scalar field f
\bigtriangledown f