diff --git a/src/cco-extensions/ModalRelationOntology.ttl b/src/cco-extensions/ModalRelationOntology.ttl
index 0b912c3..fe193cd 100644
--- a/src/cco-extensions/ModalRelationOntology.ttl
+++ b/src/cco-extensions/ModalRelationOntology.ttl
@@ -2889,6 +2889,7 @@ mro:ont00001995 rdf:type owl:ObjectProperty ;
                 rdfs:domain cco:ont00001262 ;
                 rdfs:range cco:ont00001262 ;
                 rdfs:label "is parent of"@en ;
+                skos:definition "x is_parent_of y is a primitive familial relationship between an instance of Person x and a different instance of Person y."
                 cco:ont00001760 <https://www.commoncoreontologies.org/ModalRelationOntology> .