For words that have only three letters, there is absolutely no 4th letter. For example with the word “add”, there aren't any a lot more letters afterwards and thus needs to be the word "add". The word “addict” is in the BIP39 wordlist however, you might have applied “addi” for https://freebookmarkpost.com/story19346863/examine-this-report-on-bip39-passphrase