For words that have only three letters, there is not any 4th letter. One example is with the word “include”, there isn't any far more letters afterwards and so need to be the word "insert". The word “addict” is in the BIP39 wordlist but you would have utilized “addi” for https://canvas.instructure.com/eportfolios/3396498/ricardooxtv236/opening-the-world-of-bip39-a-comprehensive-overview-to-mnemonic-expressions-and-word-checklists