For words that only have three letters, there is no 4th letter. For instance with the word “incorporate”, there are no a lot more letters Later on and thus should be the word "include". The word “addict” is inside the BIP39 wordlist however , you would've applied “addi” for “addict”. https://bookmarkgenious.com/story18975707/considerations-to-know-about-bip39-word-list-pdf