Each concept here is mapped to its prerequisites — the ideas you'd need first to understand it — all the way down to four foundations: Space, Time, Energy, Pattern. Click any prerequisite to drill down, or scroll for the chain graph.
External reference — all senses of the word “ledger” on Wiktionary. This atlas concept maps to only the slice of meaning relevant to the prerequisite graph.
A ledger is a permanent record or log that tracks all transactions, changes, or events in a system, often used in accounting, blockchain, and audit trails.