Jet is related to Missile. Missile is related to Bomb. Bombing is a form of Bomb. 
Tree is etymologically related to True. Tree is related to Shelter. Refuge is a type of Shelter. Refugee is derived from Refuge. 
Jet <--RelatedTo--> Missile <--RelatedTo--> Bomb <--FormOf-- Bombing 
True <--EtymologicallyRelatedTo-- Tree <--RelatedTo--> Shelter <--IsA-- Refuge <--DerivedFrom-- Refugee 