For words that have only 3 letters, there is absolutely no 4th letter. By way of example with the word “incorporate”, there aren't any additional letters afterwards and so needs to be the word "include". The word “addict” is in the BIP39 wordlist however , you would've applied “addi” for https://bookmarkdistrict.com/story19222575/examine-this-report-on-bip39-mnemonic-phrase-tool