noun
director; trustee; board member
A member of a board or governing body of an organization, such as a company, foundation, or school. Often used in formal titles like 理事長 (chairperson).
彼は学校法人の理事に就任した。
He was appointed as a trustee of the educational foundation.
理事会は来月開催される予定だ。
The board meeting is scheduled to be held next month.
Sino-Japanese compound of 理 (reason, principle) and 事 (matter, affair), originally referring to one who manages affairs according to principles.