Bull is a type of Animal. Bull is a type of Policeman. Policeman is related to Enforcement. 
Side is a type of Cut. Cut is related to Would. Would is the opposite of Could. 
Animal <--IsA-- Bull --IsA--> Policeman <--RelatedTo--> Enforcement 
Side --IsA--> Cut <--RelatedTo--> Would <--Antonym--> Could 