is narrower than leaf node

@prefix dct: <http://purl.org/dc/terms/> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix sio: <http://semanticscience.org/resource/> .

sio:isNarrowerThan a owl:ObjectProperty ;
    rdfs:label "is narrower than"@en ;
    dct:description "A is narrower than B iff the meaning of term A is narrower in scope than the meaning of term B"@en ;
    sio:equivalentTo "http://www.w3.org/2004/02/skos/core#broader" ;
    rdfs:isDefinedBy <http://semanticscience.org/ontology/sio/v1.53/sio-subset-labels.owl> ;
    rdfs:subPropertyOf sio:isNarrowerThant ;
    owl:inverseOf sio:isBroaderThan .