For words that have only 3 letters, there is not any 4th letter. One example is with the word “include”, there isn't any extra letters afterwards and so should be the word "include". The word “addict” is from the BIP39 wordlist but you would have utilised “addi” for “addict”. This https://socialwebleads.com/story5074273/considerations-to-know-about-bip39-word-list-pdf