For words that only have three letters, there isn't any 4th letter. For example with the word “add”, there are no far more letters afterwards and thus needs to be the word "insert". The word “addict” is from the BIP39 wordlist however, you would've utilised “addi” for “addict”. - Lưu https://friendlybookmark.com/story19502521/an-unbiased-view-of-bip39-seed-phrase-github