For words that only have three letters, there isn't a 4th letter. As an example with the word “increase”, there isn't any a lot more letters Later on and so have to be the word "insert". The word “addict” is inside the BIP39 wordlist however you might have utilised “addi” https://techonpage.com/story4187514/top-guidelines-of-bip39-word-list-pdf