For words that only have 3 letters, there is no 4th letter. For example with the word “add”, there isn't any a lot more letters afterwards and so needs to be the word "insert". The word “addict” is during the BIP39 wordlist however you would've applied “addi” for “addict”. gravity https://friendlybookmark.com/story18931392/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition