For words that only have 3 letters, there isn't a 4th letter. For instance with the word “add”, there won't be any a lot more letters Later on and so should be the word "incorporate". The word “addict” is inside the BIP39 wordlist however you would have made use of https://thesocialroi.com/story9281508/bip39-phrase-generator-can-be-fun-for-anyone