For words that have only three letters, there isn't a 4th letter. As an example with the word “add”, there isn't any a lot more letters Later on and so should be the word "insert". The word “addict” is while in the BIP39 wordlist however you would have applied “addi” https://ztndz.com/story21850067/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting