diff --git a/xml/System/Double.xml b/xml/System/Double.xml
index e2bd010481a..95942446570 100644
--- a/xml/System/Double.xml
+++ b/xml/System/Double.xml
@@ -2947,7 +2947,7 @@ This method correctly handles floating-point values and so `2.0` and `3.0` will
       </Parameters>
       <Docs>
         <param name="d">A double-precision floating-point number.</param>
-        <summary>Determines whether the specified value is normal.</summary>
+        <summary>Determines whether the specified value is not NaN, not infinite, not subnormal, and not zero.</summary>
         <returns>
           <see langword="true" /> if the value is normal; <see langword="false" /> otherwise.</returns>
         <remarks>This effectively checks the value is not NaN, not infinite, not subnormal, and not zero.</remarks>