For words that have only 3 letters, there's no 4th letter. By way of example with the word “add”, there won't be any a lot more letters Later on and therefore have to be the word "increase". The word “addict” is from the BIP39 wordlist but you might have utilized https://ilovebookmarking.com/story19471175/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool