For words that have only three letters, there is not any 4th letter. For example with the word “include”, there aren't any additional letters afterwards and thus should be the word "add". The word “addict” is inside the BIP39 wordlist but you might have utilized “addi” for “addict”. Discovering one https://total-bookmark.com/story19344893/5-simple-techniques-for-bip39-word-list-pdf