Let $(X,\tau)$ be a topological space and $\alpha,
\beta:P(X)\rightarrow P(X)$ be operators associated to $\tau$, 
we introduce the concept of  $(\alpha,\beta)$-semi open sets 
and  new generalized forms of separations 
by  ($\alpha$,$\beta$)-semi open sets. Also, 
we analyze the relations with some well known separation notions.