Base is a synonym of Bottom. Bottom is the opposite of Side. 
Salt is related to Chemical. Acid is a type of Chemical. Acid is a type of Compound. Compound is a synonym of Agree. 
Base <--Synonym--> Bottom <--Antonym--> Side 
Salt <--RelatedTo--> Chemical <--IsA-- Acid --IsA--> Compound <--Synonym--> Agree 