1. :default CSS pseudo-class

    The `:default` pseudo-class matches checkboxes and radio buttons which are checked by default, `<option>`s with the `selected` attribute, and the default submit button (if any) of a form.

  2. :indeterminate CSS pseudo-class

    The `:indeterminate` pseudo-class matches indeterminate checkboxes, indeterminate `<progress>` bars, and radio buttons with no checked button in their radio button group.

  3. radionodelist api

  4. radionodelist api: value

  5. css property: appearance: radio

  6. css selector: `:indeterminate`: applies to `<input type="radio">` elements

  7. html element: input: `type="radio"`