diff --git a/src/pyplaml/relation.py b/src/pyplaml/relation.py
index 5435e6412d7657689cb56cef34acdac18d6d0f98..4a4540f910c95b8d8875c9f922af685d421c186d 100644
--- a/src/pyplaml/relation.py
+++ b/src/pyplaml/relation.py
@@ -2,6 +2,8 @@ from enum import Enum
 
 
 class Relation(Enum):
+    """Represents a relation between diagram objects."""
+
     NONE = 0
     EXTENSION = 1
     ASSOCIATION = 2