diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index 806e492..4532011 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -78,7 +78,7 @@ Historically, even shorter 32-bit identifiers were used, like this: `2455 4239`,
 
 ### Primary key
 
-The OpenPGP primary key is a distinct component key that serves a central role in an OpenPGP certificate:
+The OpenPGP primary key is a component key that serves a distinct, central role in an OpenPGP certificate:
 
 - Its fingerprint acts as the unique identifier for the entire OpenPGP certificate.
 - It facilitates lifecycle operations, such as adding or invalidating subkeys or identities within a certificate.