noun
self-identity; personal identity
A formal, somewhat academic term referring to the sense of being a consistent, unified self over time. Often used in psychology and philosophy.
青年期には自己同一性の確立が重要な課題となる。
Establishing self-identity becomes an important task during adolescence.
アイデンティティ is a more common, everyday loanword for 'identity', while 自己同一性 is a formal, technical term used mainly in academic contexts.
Compound of 自己 (self) + 同一性 (identity, sameness). The term is a calque from Western psychology and philosophy, likely from English 'self-identity' or German 'Ich-Identität'.