contents; things inside
Refers to the material items or substances contained within something, such as a box, bag, stomach, or package.
箱の内容物を確認してください。
Please check the contents of the box.
胃の内容物を調べる検査がある。
There is a test that examines the stomach contents.
Compound of 内容 (ないよう, 'content') and 物 (ぶつ, 'thing'). The reading ぶつ is a standard Sino-Japanese reading for 物 in compounds.