For words that only have three letters, there is no 4th letter. By way of example with the word “increase”, there won't be any a lot more letters Later on and so have to be the word "include". The word “addict” is in the BIP39 wordlist however, you would've employed https://highkeysocial.com/story4306727/bip39-phrase-generator-can-be-fun-for-anyone