For words that have only three letters, there's no 4th letter. As an example with the word “include”, there are no a lot more letters afterwards and thus need to be the word "incorporate". The word “addict” is during the BIP39 wordlist however you would've utilized “addi” for “addict”. Using https://wearethelist.com/story20839628/top-latest-five-bip39-words-urban-news