Wet is related to Drink. Drink is the opposite of Coffee. Coffee is a type of Liquid. Spill is a type of Liquid. 
Letter is related to Size. Size is a type of Situation. 
Wet <--RelatedTo--> Drink <--Antonym--> Coffee --IsA--> Liquid <--IsA-- Spill 
Letter <--RelatedTo--> Size --IsA--> Situation 