Bip39 vs bip84 https://writeablog.net/ipennywpzc/the-ultimate-overview-to-offline-bip39-generators-remain-secure Though it employs BIP32 approach you may even now import BIP39 seeds into Electrum wallet. Also aside from BIp32 there is BIP44 Variation which some wallet use for the technology of seeds. For words that only have three letters, there's no 4th letter. For instance with https://bookmarkforce.com/story20681572/bip39-all-words-bip39-ian-coleman-for-dummies-https-x-com-tundra838554