For words that only have 3 letters, there is absolutely no 4th letter. Such as with the word “add”, there aren't any a lot more letters Later on and therefore should be the word "add". The word “addict” is inside the BIP39 wordlist but you would've made use of “addi” https://ariabookmarks.com/story4517704/examine-this-report-on-bip39-passphrase