For words that have only 3 letters, there is not any 4th letter. For instance with the word “add”, there are no much more letters afterwards and therefore need to be the word "increase". The word “addict” is in the BIP39 wordlist however , you would have employed “addi” for https://xyzbookmarks.com/story18645254/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39