Government is derived from Govern. Government is related to Tax. Tax is related to Property. Property is related to Example. 
Cast is related to Iron. Irony is derived from Iron. 
Govern <--DerivedFrom-- Government <--RelatedTo--> Tax <--RelatedTo--> Property <--RelatedTo--> Example 
Cast <--RelatedTo--> Iron <--DerivedFrom-- Irony 