For words that have only three letters, there is absolutely no 4th letter. As an example with the word “add”, there are no a lot more letters Later on and thus need to be the word "incorporate". The word “addict” is in the BIP39 wordlist but you would have made https://ilovebookmarking.com/story18821725/examine-this-report-on-bip39-mnemonic-phrase-tool