For words that only have 3 letters, there's no 4th letter. As an example with the word “increase”, there isn't any additional letters afterwards and thus need to be the word "add". The word “addict” is while in the BIP39 wordlist however you would have made use of “addi” for http://remingtonjszi611.almoheet-travel.com/from-words-to-wide-range-how-to-efficiently-use-bip39-passphrases-for-your-copyright-wallets