How no words occur multiple times? ^^ I dont get it

I’m currently doing a vocabulary app to practice.
Now, however, I am faced with a riddle which I can not solve.
And it should work like this:
If a word has already occurred, it should not appear random again. And only those who have not appeared yet should appear.

The words are all stored in a list.
And from this a word is randomly displayed

Maybe it will be easy, but I can not get it … :sweat_smile:

Thanks in advance!

Store all words that was returned by random in a other list.
Then check if the word exist there.
If the word exist, ignore it.
If the word not exist do whatever you want to do.