For words that only have three letters, there is not any 4th letter. By way of example with the word “increase”, there aren't any much more letters Later on and thus has to be the word "include". The word “addict” is in the BIP39 wordlist however , you would've utilised https://hylistings.com/story20298986/examine-this-report-on-bip39-mnemonic-phrase-tool