diff --git a/doc/manual/src/package-management/terminology.md b/doc/manual/src/package-management/terminology.md
index 28e2a1f0b..1722a9fc8 100644
--- a/doc/manual/src/package-management/terminology.md
+++ b/doc/manual/src/package-management/terminology.md
@@ -25,3 +25,5 @@ is true:
 - the realisation is signed by one of the `trusted-public-key`s
 - the substituter is in the `trusted-substituters` list
 - the `no-require-sigs` option has been set to disable signature checking
+- the derivation is a fixed-output derivation
+