For words that have only 3 letters, there isn't any 4th letter. For instance with the word “add”, there aren't any a lot more letters Later on and therefore must be the word "increase". The word “addict” is inside the BIP39 wordlist however you would have made use of “addi” https://yoursocialpeople.com/story4863424/top-guidelines-of-bip39-word-list-pdf