Minor

A person who is below the age of majority, consent, criminal responsibility or other adult responsibilities and accountabilities.

"It is illegal to sell weapons to minors under the age of eighteen."

A subject area of secondary concentration of a student at a college or university, or the student who has chosen such a secondary concentration.

"I became an English minor."

Determinant of a square submatrix

(British slang) A younger brother (especially at a public school).

To choose or have an area of secondary concentration as a student in a college or university.

"I had so many credit hours of English, I decided to minor in it."

Of little significance or importance.

"The physical appearance of a candidate is a minor factor in recruitment."

Of a scale which has lowered scale degrees three, six, and seven relative to major, but with the sixth and seventh not always lowered

"a minor scale"

Being the smaller of the two intervals denoted by the same ordinal number