Popup definitions and popup links

Hi Sal,

There are some topics in test lectures that I am studying but I realize that I am not familiar with some of the terminologies already explained in other or previous lectures. I don't know if this suggestion was already made or done but is it possible to add a feature where there is: 
1. A dictionary of math or subject terminologies?
2. Have the meanings pop up when the terminology is moused over?
3. hyperlink the terminology to its first reference and explanation in the text lectures?

Thanks