For words that only have three letters, there's no 4th letter. For instance with the word “insert”, there aren't any additional letters afterwards and therefore have to be the word "increase". The word “addict” is inside the BIP39 wordlist however , you would have applied “addi” for “addict”. bip39-phrase.com is https://peakbookmarks.com/story19685250/top-latest-five-bip39-words-urban-news