For words that only have three letters, there is no 4th letter. One example is with the word “include”, there isn't any a lot more letters afterwards and therefore must be the word "insert". The word “addict” is within the BIP39 wordlist but you would have applied “addi” for “addict”. https://todaybookmarks.com/story18970731/top-latest-five-bip39-seed-phrase-mnemonics-generator-urban-news