Service is related to Duty. Duty is related to Reason. Reason is a synonym of Understanding. 
Fragment is related to Word. Word is related to Construct. Structure is etymologically related to Construct. 
Service <--RelatedTo--> Duty <--RelatedTo--> Reason <--Synonym--> Understanding 
Fragment <--RelatedTo--> Word <--RelatedTo--> Construct <--EtymologicallyRelatedTo-- Structure 