Double is a type of Function. Function is a type of Relation. 
Similarity is related to Compare. Compare is a type of Analyze. Analyze is a synonym of Examine. Examine is a type of Question. 
Double --IsA--> Function --IsA--> Relation 
Similarity <--RelatedTo--> Compare --IsA--> Analyze <--Synonym--> Examine --IsA--> Question 