My suggestion is the following : Remember the word with wich we have used the dictionnary or the translator.
Scenario : When we read a book, there are some words we do not know the signification or the translation, we touch the word, then the dictionnary appears, and it will be good to have an "add button" to a specific word's list.
2 kind of possible list :
- Translation one
- Explanation one
With this feature, we will be able to view all words we didn't know with the translation or the explanation. Like this, we can remember and learn words.