Topic is a synonym of Issue. Issue is related to Item. 
Speculation is a synonym of Guess. Guess is a synonym of Hazard. Hazard is a synonym of Venture. Risk is a type of Venture. 
Topic <--Synonym--> Issue <--RelatedTo--> Item 
Speculation <--Synonym--> Guess <--Synonym--> Hazard <--Synonym--> Venture <--IsA-- Risk 