For words that have only 3 letters, there is not any 4th letter. By way of example with the word “include”, there won't be any additional letters Later on and thus needs to be the word "incorporate". The word “addict” is within the BIP39 wordlist however , you would have https://extrabookmarking.com/story18823272/not-known-factual-statements-about-bip39-explained