Silence is the opposite of Voice. Voice is related to Phone. Phone is related to Communication. Rhetoric is a type of Communication. 
one thing you do when you Buy is Pay. Pay is related to Say. Say is related to Count. 
Silence <--Antonym--> Voice <--RelatedTo--> Phone <--RelatedTo--> Communication <--IsA-- Rhetoric 
Buy --HasSubevent--> Pay <--RelatedTo--> Say <--RelatedTo--> Count 