diff --git a/algebra.sty b/algebra.sty
index 47143e0..26559d1 100644
--- a/algebra.sty
+++ b/algebra.sty
@@ -55,3 +55,6 @@
 
 \newcommand{\iiff}{\item[$\iff$]}
 \hypersetup{colorlinks, linkcolor=red}
+
+
+\def\existsone{\exists!}