Girlfriend is a type of Lover. Boyfriend is a type of Lover. Boyfriend is a type of Single. 
Bicycle is made of Metal. Metal is related to Coin. Coin is related to Term. 
Girlfriend --IsA--> Lover <--IsA-- Boyfriend --IsA--> Single 
Bicycle --MadeOf--> Metal <--RelatedTo--> Coin <--RelatedTo--> Term 