Sexy is similar to Hot. Hot is related to Fever. Fever is related to Ill. Illness is derived from Ill. 
Silent is related to Quiet. Quiet is the opposite of Say. Say is related to Nation. Nation is related to Sovereignty. 
Sexy <--SimilarTo--> Hot <--RelatedTo--> Fever <--RelatedTo--> Ill <--DerivedFrom-- Illness 
Silent <--RelatedTo--> Quiet <--Antonym--> Say <--RelatedTo--> Nation <--RelatedTo--> Sovereignty 