Buy is a type of Believe. Buy is related to Best. Best is related to Being. Being is related to Wash. 
Informal is a different concept from Formal. Formal is related to Gentleman. 
Believe <--IsA-- Buy <--RelatedTo--> Best <--RelatedTo--> Being <--RelatedTo--> Wash 
Informal <--DistinctFrom--> Formal <--RelatedTo--> Gentleman 