For words that have only 3 letters, there's no 4th letter. By way of example with the word “include”, there isn't any a lot more letters Later on and so have to be the word "include". The word “addict” is in the BIP39 wordlist however , you might have used https://bookmarksea.com/story18882640/facts-about-bip39-seed-phrase-word-list-revealed