Position is a synonym of Situation. Environment is a type of Situation. Environment is related to Conservation. 
Pure is the opposite of Dirty. Dirty is related to Smoke. Smoke is related to Color. Color is related to Light. 
Position <--Synonym--> Situation <--IsA-- Environment <--RelatedTo--> Conservation 
Pure <--Antonym--> Dirty <--RelatedTo--> Smoke <--RelatedTo--> Color <--RelatedTo--> Light 