Add user event to notrobes UI
The event probably should happen after X seconds that a word has been stable in the interface, using a timeout or similar.
While it is possible to do it server-side, there would be far too many false positives - until a definition has stabilised there is no way of knowing whether that was the word the learner is looking for or just an intermediate result.
It is true that intermediate results will also be seen so should probably be taken into account somehow, and likely wouldn't represent a significant amount of data but at the moment the strength of the signal is likely not large enough to warrant. This needs to be discussed with someone!