For words that only have three letters, there isn't a 4th letter. One example is with the word “insert”, there aren't any additional letters afterwards and so needs to be the word "increase". The word “addict” is while in the BIP39 wordlist however you would've utilized “addi” for “addict”. Retail https://apollobookmarks.com/story18894076/a-review-of-bip39-phrase-list