diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index 42dff2e..986cc14 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -76,7 +76,7 @@ The fingerprint of our example OpenPGP component key is `C0A5 8384 A438 E5A1 4F7
 For example, an OpenPGP version 4 certificate with the fingerprint `B3D2 7B09 FBA4 1235 2B41 8972 C8B8 6AC4 2455 4239` might be referenced by the 64-bit Key ID `C8B8 6AC4 2455 4239` or formatted as `0xC8B86AC424554239`.  
 Historically, even shorter 32-bit identifiers were used, like this: `2455 4239`, or `0x24554239`. Such identifiers still appear in very old documents about PGP. However, [32-bit identifiers have been long deemed unfit for purpose](https://evil32.com/). At one point, 32-bit identifiers were called "short Key ID," while 64-bit identifiers were referred to as "long Key ID."
 
-Component keys are used in one of two roles: either as "OpenPGP primary key" or as an "OpenPGP subkey."
+### Primary key
 
 The OpenPGP primary key is a distinct component key that serves a central role in an OpenPGP certificate: