～内
～ない · ～nai · JLPT N2 · noun
inside
📦 内 = 冂 enclosure + 人 person: a person who has gone inside
As a suffix, ～内 (nai) marks something within a limit: 社内 shanai, inside the company; 国内 kokunai, inside the country; 時間内 jikannai, within the time. The kanji shows a person 人 entering a frame 冂.
内 — enclosure 冂 + enter 入
内 originally depicted something entering (入) into an enclosed space (冂), giving the core sense of 'inside' or 'within'. The pictographic image of going into a covered area extended naturally to meanings like inner, internal, and inland. It contrasts with 外 ('outside').