Trade is related to People. People is related to Surprise. 
Boyfriend is a type of Lover. Boyfriend is a synonym of Fellow. Fellow is the opposite of Stranger. Stranger is a different concept from Friend. 
Trade <--RelatedTo--> People <--RelatedTo--> Surprise 
Lover <--IsA-- Boyfriend <--Synonym--> Fellow <--Antonym--> Stranger <--DistinctFrom--> Friend 