main job; principal occupation
Refers to one's primary profession or regular work, as opposed to a side job or hobby.
His main job is a teacher, but he works part-time at a café on weekends.
professional; expert; specialist
Used for someone who does something at a professional level, often implying skill beyond that of an amateur. Can also be used attributively (e.g., 本職の料理人).
His guitar skills are on a professional level.
I learn cooking from a professional chef.
A formal, somewhat old-fashioned first-person pronoun used by government officials, police officers, or other public servants when speaking in an official capacity. Not used in everyday conversation.
I will handle this matter with responsibility.
He has music as his main profession.
He is a professional chef.
I intend to handle this matter with care.