For words that only have 3 letters, there's no 4th letter. For instance with the word “add”, there won't be any far more letters afterwards and thus have to be the word "add". The word “addict” is in the BIP39 wordlist however you would have utilised “addi” for “addict”. Unlock https://minibookmarks.com/story18817174/bip39-seed-phrase-fundamentals-explained