For words that only have three letters, there's no 4th letter. One example is with the word “include”, there aren't any much more letters afterwards and so have to be the word "include". The word “addict” is during the BIP39 wordlist however you would have applied “addi” for “addict”. bip39-phrase.com https://dftsocial.com/story19578209/helping-the-others-realize-the-advantages-of-bip39-seed-phrase-mnemonics-generator