Explain is related to Help. Help is the opposite of Injure. 
Derive is a type of Evolve. Evolve is related to Change. Spot is a type of Change. Spot is a type of Fish. 
Explain <--RelatedTo--> Help <--Antonym--> Injure 
Derive --IsA--> Evolve <--RelatedTo--> Change <--IsA-- Spot --IsA--> Fish 