noun
company owner; head of a company
Refers to the proprietor or chief executive of a company, often used in formal or business settings.
彼は小さな会社の社主として、毎日忙しく働いている。
As the owner of a small company, he works busily every day.
社主の判断で新しい事業を始めることになった。
It was decided by the head of the company to start a new business.