For words that have only three letters, there isn't a 4th letter. One example is with the word “incorporate”, there won't be any far more letters afterwards and so need to be the word "include". The word “addict” is during the BIP39 wordlist however , you would have applied “addi” https://sociallawy.com/story9133319/the-definitive-guide-to-bip39-seed-phrase