Bip39 Mnemonic To Seed Some words are shorter than four letters, such as the word “act”. Other words are longer than 4 letters, including “summary”. Just one set of mnemonic can be employed to produce various addresses. This process of making account was introduced in BIP32 & BIP39 while ago. https://bookmarkingalpha.com/story18569108/bip39-flutter-not-known-details-about-bip39-word-list