Theoretical is the opposite of Actual. Actual is related to Being. 
Interior is related to Design. Design is related to Works. Works is a synonym of Plant. Plant is the opposite of Tree. 
Theoretical <--Antonym--> Actual <--RelatedTo--> Being 
Interior <--RelatedTo--> Design <--RelatedTo--> Works <--Synonym--> Plant <--Antonym--> Tree 