∂

The character ∂ (html element: ∂ or ∂, unicode: U+2202) or $\partial$ is a stylized d mainly used as a mathematical symbol to denote a partial derivative such as $\frac{\partial z}{\partial x}$ (read as "the partial derivative of z with respect to x"). The symbol was originally introduced by Legendre in 1786, but only gained popularity when it was used by Jacobi in 1841.

∂ is also used to denote the following:

• The Jacobian, $\frac{\partial(x, y, z)}{\partial(u, v, w)}$.
• The boundary of a set in topology.
• The boundary operator on a chain complex in homological algebra.
• The boundary operator of a differential graded algebra.
• The Dolbeault operator on complex differential forms.

The symbol may be referred to as "del", "dee", "partial dee", "partial", "curly dee", or "dabba".