For words that have only 3 letters, there isn't any 4th letter. By way of example with the word “increase”, there aren't any much more letters Later on and therefore should be the word "insert". The word “addict” is inside the BIP39 wordlist however you might have used “addi” for https://telebookmarks.com/story9203875/top-guidelines-of-bip39-word-list-pdf