For words that only have three letters, there isn't a 4th letter. By way of example with the word “add”, there are no more letters Later on and thus need to be the word "include". The word “addict” is during the BIP39 wordlist however, you might have utilised “addi” for https://pukkabookmarks.com/story19019578/5-essential-elements-for-bip39-explained