1 files changed, 5 insertions, 0 deletions
diff --git a/library/topology/basis.tex b/library/topology/basis.tex
index dda187c..bca42f0 100644
--- a/library/topology/basis.tex
+++ b/library/topology/basis.tex
@@ -43,3 +43,8 @@
     for all $U, V, x$ such that $U, V\in B$ and $x\in U,V$
     there exists $W\in B$ such that $x\in W\subseteq U, V$.
 \end{definition}
+
+\begin{definition}\label{genOpens}
+    $\genOpens{B}{X} = \{ U\in\pow{X} \mid for all $x\in U$ there exists $V\in B$
+    such that $x\in V\subseteq U$\}$.
+\end{definition}