_hypernym(x,y) implies _hypernym(y,x)
_derivationally_related_form(x,y) implies _derivationally_related_form(y,x)
_member_meronym(x,y) implies _member_meronym(y,x)
_has_part(x,y) implies _has_part(y,x)
_synset_domain_topic_of(x,y) implies _synset_domain_topic_of(y,x)
