Junior. (See also the heraldic term cadency.)
A younger or youngest son, who would not inherit as a firstborn son would.
A young gentleman learning sheep farming at a station; also, any young man attached to a sheep station.
A participant in a cadetship.
A student at a military school who is training to be an officer.
Used other than figuratively or idiomatically: see younger, brother. (This entry is a translation hub.)