Bip39 Passphrase Empty For None ) Some words are shorter than 4 letters, such as the word “act”. Other words are extended than 4 letters, for example “summary”. 1 list of mnemonic can be utilized to create many addresses. This process of making account was introduced in BIP32 & BIP39 https://ok-social.com/story4013508/bip39-rules-the-smart-trick-of-bip39-phrase-that-nobody-is-discussing