diff --git a/book/source/glossary.md b/book/source/glossary.md
index ae47e74..c0a3bd5 100644
--- a/book/source/glossary.md
+++ b/book/source/glossary.md
@@ -32,7 +32,9 @@ Authentication
     The term "authentication" here is semantically different from the one used in {term}`Authentication Key Flag`.
 
 Authentication Key Flag
-    A {term}`Key Flag`, which indicates that a {term}`Component Key` can be used to confirm control over {term}`private key material` against a remote system. This is typically done to perform an authorative action, like logging into a system. The term "authentication" here is semantically different from {term}`Authentication`. See [](key-flags).
+    A {term}`Key Flag` which indicates that a {term}`Component Key` can be used to prove control over {term}`private key material` with a challenge-response mechanism. This is typically done to log into a remote system, often using the OpenSSH protocol.
+
+    Note that the term "authentication" is used in a different context here than {term}`Authentication` of {term}`identity claims<identity claim>` that are associated with a {term}`certificate`. See [](key-flags).
 
 Authentication Tag
     See {term}`Message Authentication Code`.