noun
sub-screen; pop-up window; child window
Computing term for a secondary window or screen that appears within or alongside a main interface, such as a pop-up, dialog, or inset video feed.
設定を変更するには、子画面を開いてください。
To change the settings, please open the sub-screen.
ビデオ通話中に子画面で資料を共有できる。
During a video call, you can share materials in a pop-up window.
ポップアップ is a common loanword for a pop-up window, often used interchangeably with 子画面 in casual contexts, but 子画面 is more technical and can refer to any embedded secondary screen.
Compound of 子 (こ, 'child') and 画面 (がめん, 'screen'), literally 'child screen'. A straightforward technical term formed from existing kanji.