Overlays & Surfaces
Modal
also known as modal window, modal overlay
Modal describes a behavior: the interface enters a special mode where the background is disabled and you must respond to the foreground before continuing. It usually appears with a scrim dimming everything behind it. 'Modal' is an adjective more than a component, though people often say 'a modal' to mean a modal dialog.
See it live — shadcn/ui · MUI · Ant Design
Don't confuse it with
Modal is a behavior (blocks the background), not a component. A dialog is a component. 'Modal dialog' = a dialog behaving modally. A popover is the opposite of modal: it's lightweight and leaves the background usable.
In the wild
A cookie-consent window you must accept or reject before using a site behaves as a modal.