Real is the opposite of Potential. Potential is related to Danger. Danger is related to Concept. 
Used is related to Familiar. Familiar is related to Know. Know is a synonym of Acknowledge. 
Real <--Antonym--> Potential <--RelatedTo--> Danger <--RelatedTo--> Concept 
Used <--RelatedTo--> Familiar <--RelatedTo--> Know <--Synonym--> Acknowledge 