In English language naming cnventions, "Junior" means that that person has the same name as a living member of his family in an older generation, usually his father.
Junior.
Basketball Junior PLayers
Park Hill Junior School
JCS = Junior Commissioned Secretary
United States Junior Mathematical Olympiad
junior educated rich kid j.e.r.k
Junior Reserve Officer Training Corps
If followed by ROTC, the NJ stands for Naval Junior.
Naval Junior Reserve Officer Training Corps.
Junior Operatives Networking as Spies.
JROTC is an acronym for Junior Reserve Officers' Training.
Junior, meaning that a person with this name was named after their father (usually).