Bip39 ozon https://www.gamespot.com/profile/pothirpeib/ While it takes advantage of BIP32 process you can even now import BIP39 seeds into Electrum wallet. Also in addition to BIp32 There's BIP44 version which some wallet use for the generation of seeds. For words that have only 3 letters, there isn't a 4th letter. As https://todaybookmarks.com/story20830710/bip39-gpu-not-known-factual-statements-about-bip39-mnemonic-https-www-youtube-com-channel-ucupxfytj0fb78sq55hu6ocw