noun, noun which may take the genitive case particle 'no'
Refers to something that belongs to or concerns oneself, often used in formal or written contexts. Can modify nouns with の.
これは一己の問題だ。
This is a personal matter.
一己の利益を優先してはいけない。
You must not prioritize your own interests.
The exact derivation is uncertain; the kanji 一 (one) and 己 (self) combine to suggest 'one's own self'.