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.
A grade is a mark or level assigned based on performance or quality, but this definition is incomplete without a deeper understanding of the evaluation process.
External reference — all senses of the word “grade” on Wiktionary. This atlas concept maps to only the slice of meaning relevant to the prerequisite graph.