For words that only have 3 letters, there is no 4th letter. For example with the word “incorporate”, there aren't any more letters afterwards and so need to be the word "incorporate". The word “addict” is inside the BIP39 wordlist however, you would've utilized “addi” for “addict”. Artwork can be https://digibookmarks.com/story18951817/the-invalid-bip39-phrase-diaries