Subject is the opposite of Citizen. Citizen is related to Identity. 
Lost is related to Missing. Missing is related to Lose. Lose is related to Fit. Joint is a type of Fit. 
Subject <--Antonym--> Citizen <--RelatedTo--> Identity 
Lost <--RelatedTo--> Missing <--RelatedTo--> Lose <--RelatedTo--> Fit <--IsA-- Joint 