For words that only have 3 letters, there is not any 4th letter. As an example with the word “include”, there aren't any far more letters afterwards and thus need to be the word "add". The word “addict” is while in the BIP39 wordlist however, you would have made use https://naturalbookmarks.com/story19524404/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting