schema (n.)

plural schemata, 1796, in Kantian philosophy ("a product of the imagination intermediary between an image and a concept"), from Greek skhema "figure, appearance, the nature of a thing," related to skhein "to get," and ekhein "to have, hold; be in a given state or condition," from PIE root *segh- "to hold." Meaning "diagrammatic representation" is from 1890; general sense of "hypothetical outline" is by 1939.