diff --git a/man7/capabilities.7 b/man7/capabilities.7
index 839b16763..ce4bce6c4 100644
--- a/man7/capabilities.7
+++ b/man7/capabilities.7
@@ -962,9 +962,11 @@ with version 2 capabilities, but serve a different purpose:
 to support namespaced file capabilities (described below).
 As with version 2 file capabilities,
 the capability masks are 64 bits in size.
-In addition, the namespace root user ID is encoded in the
+In addition, the root user ID of namespace is encoded in the
 .I security.capability
 extended attribute.
+(A namespace's root user ID is the value that user ID 0
+inside that namespace maps to in the initial user namespace.)
 .\"
 .SS Transformation of capabilities during execve()
 .PP