Slavery is a type of Practice. Training is a type of Practice. 
Gain is etymologically related to Wide. Gain is the opposite of Lose. Drop is a type of Lose. Drop is a synonym of Abandon. 
Slavery --IsA--> Practice <--IsA-- Training 
Wide <--EtymologicallyRelatedTo-- Gain <--Antonym--> Lose <--IsA-- Drop <--Synonym--> Abandon 