Peak is a synonym of Tip. Tip is related to Reward. Reward is related to Police. 
Convention is a type of Practice. Ritual is a type of Practice. Ritual is related to Tradition. Tradition is a synonym of Doctrine. 
Peak <--Synonym--> Tip <--RelatedTo--> Reward <--RelatedTo--> Police 
Convention --IsA--> Practice <--IsA-- Ritual <--RelatedTo--> Tradition <--Synonym--> Doctrine 