(set theory) relative complement

(generally) difference / (arithmetic) difference

concept, general idea

(set theory) symmetric difference

an elder / a scholar / a teacher or a professor / sensei (Japanese martial arts teacher) / sir, a polite form of address to teachers, doctors, etc.

a title used after the name of teachers, doctors, lawyers, or certain other professionals

(dialect, Hakata) teacher, professor

explanation

to explain

instruction; teaching; school; lesson, class