Art is related to Creativity. Writing requires Creativity. Essay is a type of Writing. 
Meal is related to Eating. Muscle can be used for Eating. Tongue is a type of Muscle. Tongue is related to Part. 
Art <--RelatedTo--> Creativity <--HasPrerequisite-- Writing <--IsA-- Essay 
Meal <--RelatedTo--> Eating <--UsedFor-- Muscle <--IsA-- Tongue <--RelatedTo--> Part 