For words that have only three letters, there is no 4th letter. For instance with the word “include”, there won't be any far more letters afterwards and thus must be the word "include". The word “addict” is inside the BIP39 wordlist however , you would have utilized “addi” for “addict”. https://getidealist.com/story21403798/the-basic-principles-of-bip39-passphrase-generator