本職|ほんしょくhonshoku[0]heiban (flat)

1. nounprincipal occupation; main job
2. nounprofessional; an expert; specialist
   ギターでカントリー・ウエスタンを弾ひくのは本職ほんしょくのミュージシャンならごくたやすいことだ。↗

   Playing country-western music on guitar is real kid stuff to a true professional.
3. pronounI (of a government official, etc.); me

• Antonym兼業けんぎょうNeutralA side business or second line of work run alongside one's main one; neutral in register, it contrasts with 「本職」 only in the main-versus-side distinction.
• Antonym副職WrittenAntonym: a secondary post or side role held outside one's main job; written/formal prose, the counterpart of 「本職」 as the main occupation.

Use 「本職」 for one's original or main occupation, and for a true professional, as in 「本職の大工」; officials also use it for 'I' in official documents. For side jobs or secondary posts, pick 「副職」 (written/formal) or 「兼業」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 本来ほんらいの職業しょくぎょうや職務しょくむ。本業ほんぎょう。
2. 専門家せんもんか。