Contribution is derived from Contribute. Combine is a type of Contribute. Combine is derived from Combination. Combination is a synonym of Blend. 
Regular is a synonym of Just. Just is the opposite of Bad. Bad is related to Judgment. 
Contribution --DerivedFrom--> Contribute <--IsA-- Combine --DerivedFrom--> Combination <--Synonym--> Blend 
Regular <--Synonym--> Just <--Antonym--> Bad <--RelatedTo--> Judgment 