# Notation

$\ne$ - is not equal to

$\approx$ - approximately equal to

$\sim$ - is similar to; has distribution;

$\propto$ - is proportional to

$\sum$ - sum over .. from .. to ..

$\prod$ - product over .. from .. to ..

$\forall$ - for all, for any, for each

$\exists$ - there exists

$\exists!$ - there exists exactly one

$\in$ - is an element of

$\notin$ - is not an element of

$\ni$ - such that

$\Delta$ - delta, change in; Laplace operator

$\nabla$ - gradient of; divergence of; curl of

$\partial$ - partial derivative; boundary of; degree of

$\mathbb{N}$ - natural numbers (1, 2)

$\mathbb{Z}$ - integers (-1, 0, 1)

$\mathbb{Q}$ - rational (-1/2, 0.7)

$\mathbb{R}$ - real ( $\pi, \sqrt{}$ )

$\mathbb{C}$ - complex ( $1 + 2i$ )

$\delta$

$\sigma$