Courage is a type of Virtue. Courage is related to Brave. Brave is the opposite of Afraid. 
Important is similar to Serious. Serious is the opposite of Ridiculous. Ridiculous is a synonym of Funny. 
Virtue <--IsA-- Courage <--RelatedTo--> Brave <--Antonym--> Afraid 
Important <--SimilarTo--> Serious <--Antonym--> Ridiculous <--Synonym--> Funny 