For words that only have three letters, there is no 4th letter. For example with the word “add”, there isn't any far more letters afterwards and so need to be the word "insert". The word “addict” is inside the BIP39 wordlist however you might have utilised “addi” for “addict”. Meticulously https://bookmarkworm.com/story18990821/5-simple-techniques-for-bip39-word-list-pdf