Length is the opposite of Short. Shirt is etymologically related to Short. Shirt is related to Clothing. Gray is a type of Clothing. 
Alarm is related to Fire. Fire is related to Department. Department is related to Store. Store can be used for Purchase. 
Length <--Antonym--> Short <--EtymologicallyRelatedTo-- Shirt <--RelatedTo--> Clothing <--IsA-- Gray 
Alarm <--RelatedTo--> Fire <--RelatedTo--> Department <--RelatedTo--> Store --UsedFor--> Purchase 