Three categories or three classes (Tib. dé sum; Wyl. sde gsum) — the three categories into which Mañjushrimitra divided the Dzogchen teachings he received from Garab Dorje:
- the outer category of mind (semdé),
- the inner category of space (longdé), and
- the category of pith instructions (mengak dé).
- Jamgön Kongtrul, The Treasury of Knowledge, Book Six, Part Four: Systems of Buddhist Tantra, translated by Elio Guarisco and Ingrid McLeod (Ithaca: Snow Lion, 2005), pages 339-345.
- Tulku Thondup, The Practice of Dzogchen (Ithaca: Snow Lion, 1989), Part I, 'Three Divisions of Atiyoga', pages 47-88.