Theory is related to Fundamental. Fundamental is similar to Basic. Basic is related to Apple. Apple is related to Pine. 
Side is a synonym of English. English is related to Common. Common is a synonym of Widespread. 
Theory <--RelatedTo--> Fundamental <--SimilarTo--> Basic <--RelatedTo--> Apple <--RelatedTo--> Pine 
Side <--Synonym--> English <--RelatedTo--> Common <--Synonym--> Widespread 