For words that have only 3 letters, there is not any 4th letter. For example with the word “increase”, there isn't any extra letters afterwards and so have to be the word "include". The word “addict” is in the BIP39 wordlist however, you would've employed “addi” for “addict”. - Lưu https://livebackpage.com/story4198234/not-known-factual-statements-about-bip39-explained