Interval is a synonym of Separation. Separation is derived from Separate. Separate is the opposite of Connect. 
Content is related to Glass. Glass is related to Tube. Stem is a type of Tube. 
Interval <--Synonym--> Separation --DerivedFrom--> Separate <--Antonym--> Connect 
Content <--RelatedTo--> Glass <--RelatedTo--> Tube <--IsA-- Stem 