自身|じしんjishin[1]atamadaka (head-high)

1. noun, noun (suffix)(one's) self; oneself; yourself; himself; herself
   ジェーン自身じしんがこの手紙てがみを書かいた。↗

   Jane wrote the letter herself.

• Synonym自分じぶんNeutralThe everyday, most common word for oneself, as in 「自分でやる」; 「自身」 mostly attaches after a noun to stress the person themselves.
• Synonym自己じこWrittenWritten/formal prose for the self, mostly in compounds such as 「自己紹介」 and 「自己責任」.
• Synonym自分自身じぶんじしんNeutralStresses the person themselves, as in 「自分自身を見つめる」; stronger than 「自分」 alone.
• Synonym本人ほんにんNeutralThe person in question, as in 「本人確認」 or 「本人に聞く」; sets that person apart from representatives or bystanders.
• Synonym自らみずからWrittenWritten/formal prose. As おのずから, an adverb meaning 'naturally, of its own accord'; as 自ら (みずから), it means doing something in person, close to 「自身」.
• Antonym他人たにんNeutralThe opposite of 「自身」: other people, as in 「他人に頼る」.
• Antonym他者たしゃWrittenThe opposite of 「自身」 in written/formal prose: 'the other', used mainly in philosophical discussion.

Default to 「自身」 for 'the person himself/herself'. In everyday speech say 「自分」; in compounds like 「自己紹介」 use 「自己」; for the person in question use 「本人」; for extra emphasis 「自分自身」; for others 「他人」 or, in formal prose, 「他者」.

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

1. 自分じぶんそのもの、自みずから。
2. （体言たいげんに付つき、その語ごを強調きょうちょうする）その人ひと自体じたい、それ自体じたい、その物自体ものじたい。
3. （「男性だんせい自身じしん」などの形かたちで）性器せいき。