For words that only have three letters, there is no 4th letter. One example is with the word “incorporate”, there aren't any much more letters Later on and so need to be the word "incorporate". The word “addict” is in the BIP39 wordlist however , you would've applied “addi” for https://baidubookmark.com/story18718353/top-latest-five-bip39-words-urban-news