Mail is a synonym of Post. Post is related to Dead. Dead is a different concept from Survivor. Survivor is derived from Survive. 
Ground is related to Step. Step is a type of Support. 
Mail <--Synonym--> Post <--RelatedTo--> Dead <--DistinctFrom--> Survivor --DerivedFrom--> Survive 
Ground <--RelatedTo--> Step --IsA--> Support 