For words that have only 3 letters, there isn't any 4th letter. For instance with the word “increase”, there won't be any much more letters Later on and so have to be the word "add". The word “addict” is within the BIP39 wordlist however , you would have made use https://express-page.com/story4189627/ledger-seed-phrase-bip39-no-further-a-mystery