Other forms: juniors
Junior means lower in rank, or younger. A junior doctor, junior staff, junior to me by two years.
In Britain a junior school takes children from about seven to eleven, and junior on its own can mean a child of that age. In America, Junior after a name means a son with the same name as his father, abbreviated Jr, and a junior is a student in the third year of a four-year course. Note that junior takes to rather than than — junior to him, never junior than him — because it is a Latin comparative already. The opposite is senior, which behaves the same way.
1adjectivejuniorLower in rank or position.
“Two junior members of staff were left to run it.”
synonyms: subordinate, lower-ranking
2adjectivechildrenFor younger children.
“She moved up to the junior school in September.”
3nounyoungerSomebody younger or of lower rank.
“He is three years my junior.”
Too few real examples of this word to estimate which sense is commonest.
junior is a rank or age relation.
Latin junior is the comparative of juvenis, young — the same root as juvenile and rejuvenate. It arrived in English already meaning younger, which is why adding -er or than to it is wrong twice over.
Latin
junior
English, today
junior
Built from
Borrowed from Latin junior, a contraction of iuvenior (“younger”) which is the comparative of iuvenis (“young”); see juvenile.
Etymology from Wiktionary, CC BY-SA