For words that only have three letters, there is not any 4th letter. As an example with the word “include”, there aren't any extra letters afterwards and so needs to be the word "include". The word “addict” is in the BIP39 wordlist however , you might have employed “addi” for https://bookmarkgenius.com/story19354680/considerations-to-know-about-bip39-word-list-pdf