Safe is a different concept from Drop. Drop is related to Purpose. Sake is a type of Purpose. Sake is a synonym of Interest. 
Threshold is a synonym of Morning. Morning is related to Event. Event is related to Camp. Camp is related to City. 
Safe <--DistinctFrom--> Drop <--RelatedTo--> Purpose <--IsA-- Sake <--Synonym--> Interest 
Threshold <--Synonym--> Morning <--RelatedTo--> Event <--RelatedTo--> Camp <--RelatedTo--> City 