Usage patterns
〈人〉は勤勉だsomeone is diligent/hardworking
He is known as a diligent student.
勤勉に〈動詞〉to do something diligently
She works diligently every day.
勤勉な〈人〉a diligent person
He is the most diligent employee at the company.
勤勉さを〈動詞〉to evaluate/praise someone's diligence
His boss praised his diligence.
