When form fields are logically grouped together (especially radio buttons and checkboxes), non-visual users need access to both prompts. For example, in the following set of radio buttons, users need to know that "Computer Science" is a label associated with the first radio button, but that alone would not give them enough information to answer the question. They also need to know that "Select a major" is the overall prompt.

Screen shot of a set of five radio buttons, labeled Computer Science, Engineering, Economics, Physics, and Psychology. The overall prompt is 'Select a major'

In HTML, use fieldset and legend

<legend>Select a major:</legend>
<input type=“radio” name=“major” id=“maj1”>
<label for=“maj1”>Computer Science</label>
<!-- etc. -->

In PDF, use tooltip like legend

Screen shot of the same set of radio buttons in Adobe Acrobat Pro, with 'Select a major' entered into the Tooltip field in the Radio Button Properties dialog

And “Radio Button Choice” like label

Screen shot of the same set of radio buttons as in the previous image, with 'Computer Science' entered into the Radio Button Choice field