Sand is related to Grain. Wheat is a type of Grain. Wheat is related to Powder. 
Certain is related to Knowledge. Book have Knowledge. Therapy is a type of Book. 
Sand <--RelatedTo--> Grain <--IsA-- Wheat <--RelatedTo--> Powder 
Certain <--RelatedTo--> Knowledge <--HasA-- Book <--IsA-- Therapy 