For words that have only 3 letters, there is not any 4th letter. For example with the word “add”, there aren't any additional letters Later on and thus should be the word "add". The word “addict” is within the BIP39 wordlist however, you might have utilized “addi” for “addict”. - https://easiestbookmarks.com/story19111690/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39