The Personal Dictionary is made of words that you want to know in general or add to your long-term, passive vocabulary. To add a word to your personal dictionary, long press on the star (i.e., top right) and add to Personal Dictionary. In contrast to "Today's Words", Personal Dictionary may contain hundreds or even thousands of words. When adding words to your personal dictionary, you will add them to one of the groups: Noun, Verb, Adjective, Link, or Phase. It is easier to remember words in the long term when designating words by parts of speech .
The following video elaborates on the Personal Dictionary's function and daily usage:
If you directly visit the "Personal Dictionary" page, you will notice that it is split into three categories: i. Today's Words, ii. Active Dictionary, and iii. All Flagged Words.