Productive is related to Creative. Creative is related to Imagination. Imagination is related to Thought. Thanks is etymologically related to Thought. 
Lesson is part of Course. Course is a type of Hunt. 
Productive <--RelatedTo--> Creative <--RelatedTo--> Imagination <--RelatedTo--> Thought <--EtymologicallyRelatedTo-- Thanks 
Lesson --PartOf--> Course --IsA--> Hunt 