Definitely something that could be nice in an active-document.
By analogy, Wikipedia articles have a feature where, if you mouse-over a link, it'll display a preview of the link-target (https://en.wikipedia.org/wiki/Wikipedia:Tools/Navigation_pop... ). This can be an efficient way for a reader to conveniently glance at the definition of a term while reading.
Mathematical notation varies significantly between fields, and many papers define custom symbols with their own paper-specific definitions. So this sort of feature isn't just something for math-newbies, but rather something that could significantly benefit experts too.
The same sort of annotations might be more situational in non-active documents, where there'd be more of a trade-off between helpful-annotations and clutter.
By analogy, Wikipedia articles have a feature where, if you mouse-over a link, it'll display a preview of the link-target (https://en.wikipedia.org/wiki/Wikipedia:Tools/Navigation_pop... ). This can be an efficient way for a reader to conveniently glance at the definition of a term while reading.
Mathematical notation varies significantly between fields, and many papers define custom symbols with their own paper-specific definitions. So this sort of feature isn't just something for math-newbies, but rather something that could significantly benefit experts too.
The same sort of annotations might be more situational in non-active documents, where there'd be more of a trade-off between helpful-annotations and clutter.