adjective
not used before a noun US
younger in age
b - used chiefly in its abbreviated form Jr. to identify a son who has the same name as his father
always used before a noun :lower in standing or rank
always used before a noun :designed for or done by young people
noun
plural -niors
[count] a person who is younger than another person
a person who is of a lower rank than another person
a US :a student in the third of four years in a high school or college
b Brit :a student at a junior school
US informal - used like a name for a male child or son