minor in

minor in something

to study a secondary subject in college. (Compare this with major in something.) I minored in math in college. I decided to minor in history.

minor in

v.
To complete a long-term course of study in some subject that is one's secondary focus: My main course of study is biology, and I'm minoring in philosophy.
References in classic literature ?
Godfrey Ablewhite was entrusted with the care of a sum of twenty thousand pounds--as one of two Trustees for a young gentleman, who was still a minor in the year eighteen hundred and forty-eight.
Agent Ronnie Ebanks reportedly has secured weekend mounts that include Mass Media in Saturday's San Fernando Stakes and A Song in A Minor in Sunday's El Encino Stakes.
The average unaccompanied minor in the United States is fifteen years old, but some have been as young as eighteen months old.
The youth was charged with criminal trespassing, criminal mischief, theft, violating curfew and being a minor in possession of alcohol, said Oakridge police officer Sjon Clemons.
Once these upgrades are completed on May 21 (as currently scheduled), other scheduled system upgrades will be minor in comparison.