the state or quality of being identical or the same; depending on context, can also refer to personal identity.
本人の同一性を確認するために、身分証を提示してください。
Please present identification to verify the person's identity.
数学では、二つの式の同一性が重要だ。
In mathematics, the identity of two expressions is important.
文化的同一性について意見が交わされた。
Opinions were exchanged about cultural identity.