Wikipedia
Semde
Semde (; Sanskrit: cittavarga) translated as "mind division", "mind class" or "mind series" is the name of one of three scriptural and lineage divisions within Atiyoga, Dzogchen or the Great Perfection which is itself the pinnacle of the ninefold division of practice according to the Nyingma school of Tibetan Buddhism.
Semde emphasizes the clarity (gsal-ba) or the innate awareness ( rig-pa) aspect of the Natural State.
Penor Rinpoche states that due to the different approaches of various Dzogchen lineages, three sub-schools have developed of which semde is one. The other two divisions or schools are Longde (Space Series) and Menngagde (Oral Instruction Series). The Mind School is attributed to Sri Singha and Vairotsana's lineage