Regular part

 ( Complex Analysis ) 

In mathematics, the regular part of a Laurent series consists of the series of terms with positive powers.. That is, if

$f(z)\; =\; \backslash sum\_\{n=-\backslash infty\}^\{\backslash infty\}\; a\_n\; (z\; -\; c)^n,$

$\backslash sum\_\{n=0\}^\{\backslash infty\}\; a\_n\; (z\; -\; c)^n.$

In contrast, the series of terms with negative powers is the principal part.