For words that only have 3 letters, there is not any 4th letter. By way of example with the word “add”, there isn't any extra letters Later on and therefore has to be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you would've applied “addi” for https://socialskates.com/story20169114/the-basic-principles-of-bip39-passphrase-generator