For words that have only three letters, there isn't any 4th letter. By way of example with the word “insert”, there isn't any additional letters Later on and thus has to be the word "add". The word “addict” is within the BIP39 wordlist however you would've used “addi” for “addict”. https://meshbookmarks.com/story19671692/top-latest-five-bip39-seed-phrase-mnemonics-generator-urban-news