Speculation is a synonym of Guess. Guess is a synonym of Hazard. 
Opera is related to Art. Art is related to General. General is related to Veteran. Veteran is related to Military. 
Speculation <--Synonym--> Guess <--Synonym--> Hazard 
Opera <--RelatedTo--> Art <--RelatedTo--> General <--RelatedTo--> Veteran <--RelatedTo--> Military 