Joining a company; starting employment at a firm (becoming an employee).
4月に新卒で大手企業に入社した。
I joined a major company as a new graduate in April.
入社後は数週間の研修がある。
There is a several-week training period after joining the company.
入社式にはスーツを着て出席した。
I attended the company's entrance ceremony wearing a suit.