For words that have only 3 letters, there is no 4th letter. One example is with the word “incorporate”, there are no extra letters afterwards and so must be the word "include". The word “addict” is during the BIP39 wordlist however you would've utilized “addi” for “addict”. bip39-phrase.com is surely https://brightbookmarks.com/story19102382/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39