Translation guide
The main job or profession that someone does, especially as opposed to side jobs or hobbies.
principal occupation
The primary work that someone does for a living, often in contrast to part-time or secondary work.
The most common and natural way to say 'principal occupation'. It implies the main job that provides one's primary income or identity.
His principal occupation is teaching.
Similar to 本業, but often emphasizes one's professional identity or expertise. Can also mean 'professional' as opposed to amateur.
A more literal translation, often used in formal or written contexts like forms or surveys.
Please fill in your principal occupation.
A somewhat literary or traditional term for one's livelihood or trade. It carries a nuance of the work that sustains one's life.
本業 (ほんぎょう) is the most common and neutral term for one's main job. 本職 (ほんしょく) often implies professional status or expertise, and can be used to distinguish a professional from an amateur. In many contexts they are interchangeable, but 本職 can sound more formal or emphasize skill.
My main job is so busy I can't manage my side business.
彼は本職のシェフです。
He is a professional chef (that's his principal occupation).
農業を生業とする。
Farming is his principal occupation.
Writing is his principal occupation.