diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index e0ddfaf..c3b3ff1 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -6,7 +6,9 @@ SPDX-License-Identifier: CC-BY-SA-4.0
 (certificates_chapter)=
 # Certificates
 
-OpenPGP fundamentally hinges on the concept of "OpenPGP certificates," also known as "OpenPGP keys." These certificates are complex data structures essential for identity verification, data encryption, and digital signatures. Understanding their structure and function is pivotal to effectively applying the OpenPGP standard.
+OpenPGP fundamentally hinges on the concept of "OpenPGP certificates," also known as "OpenPGP public keys." These certificates are complex data structures essential for identity verification, data encryption, and digital signatures. Understanding their structure and function is pivotal to effectively applying the OpenPGP standard.
+
+An OpenPGP certificate, by definition, does not contain private key material.
 
 ## Terminology: Understanding "keys"