noun
modern history
Refers to the historical period from roughly the Meiji era onward, or the academic field studying that period.
彼は大学で近代史を専攻している。
He is majoring in modern history at university.
この博物館には近代史の展示がある。
This museum has an exhibition on modern history.
歴史 is the general term for 'history', while 近代史 specifically means 'modern history'.
Compound of 近代 (きんだい, 'modern era') and 史 (し, 'history').