For words that have only three letters, there isn't a 4th letter. One example is with the word “include”, there are no a lot more letters afterwards and thus should be the word "add". The word “addict” is during the BIP39 wordlist however, you might have employed “addi” for “addict”. https://orangebookmarks.com/story19045092/5-simple-techniques-for-bip39-word-list-pdf