Travel is related to Ride. Bus is a type of Ride. Bus is a synonym of Coach. 
Rule is related to Physics. Physics is related to Mathematics. Mathematics is related to Equal. Equal is related to Comparable. 
Travel <--RelatedTo--> Ride <--IsA-- Bus <--Synonym--> Coach 
Rule <--RelatedTo--> Physics <--RelatedTo--> Mathematics <--RelatedTo--> Equal <--RelatedTo--> Comparable 