Light is related to Walk. Walk is related to Self. Self is related to Rope. Cable is a type of Rope. 
Circuit is related to Electricity. Electricity is related to Station. Station is related to Department. 
Light <--RelatedTo--> Walk <--RelatedTo--> Self <--RelatedTo--> Rope <--IsA-- Cable 
Circuit <--RelatedTo--> Electricity <--RelatedTo--> Station <--RelatedTo--> Department 