noun
Refers to what is physically inside a container, package, bag, food, or other object. Often translated according to context as contents, interior, or filling.
箱の中身を確認してください。
Please check the contents of the box.
このパンの中
The filling in this bread is custard cream.
noun
substance; real content
Used figuratively for the meaningful substance of a speech, plan, book, person, or activity, rather than its outside appearance or form.
見た目は立派だが、中身があまりない企画だ。
It looks impressive, but the plan does not have much substance.
会議では契約の中身を詳しく話し合った。
At the meeting, we discussed the details of the contract.
noun
Only when written 中身
Specialized sword-related use referring to the blade itself. This is not the ordinary modern word for a blade in general; 刃 or 刀身 is more usual outside this limited context.
刀剣の説明で「中身」は刀の刃そのものを指すことがある。
In descriptions of swords, 中身 can refer to the blade itself.