For words that have only three letters, there isn't any 4th letter. Such as with the word “increase”, there are no more letters afterwards and thus must be the word "incorporate". The word “addict” is inside the BIP39 wordlist however, you would've applied “addi” for “addict”. In this article we’ll https://escatter11.fullerton.edu/nfs/show_user.php?userid=7804586