For words that only have 3 letters, there isn't a 4th letter. As an example with the word “include”, there aren't any more letters afterwards and so have to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however you would've utilised “addi” for “addict”. Try to https://bookmarkshome.com/story4437701/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool