Bip39 standard https://andersonsaeu988.iamarrows.com/bip39-generator-online-the-best-devices-for-secure-wallet-creation The last action of BIP-39 is building the actual binary seed which is then applied like a learn key in BIP-32 deterministic wallet or utilizing other approaches. For words that only have 3 letters, there isn't any 4th letter. One example is with the word “increase”, ... https://onlybookmarkings.com/story20562352/bip39-world-list-the-single-best-strategy-to-use-for-bip39-recovery-tool-https-linktr-ee-bip39