SDE can stand for: In culture Self Defined Ethnicity, an ethnic classification code used by the British government and police In science, medicine, and technology Screen door effect, a video display issue Sebacoyl dinalbuphine ester, an analgesic Semantic dictionary encoding Software development engineer Software development environment Spatial Database Engine (ArcSDE) Spectral density estimation Stochastic differential equation sub-divisional error, a read head error mechanism System development environment In education Self-directed education, self-learning, often synonymous with unschooling In sports Strong-side Defensive End, a position in American Football In politics Social Democratic Party (Estonia) State delegate equivalents, a part of the In transportation The IATA code for an airport in Argentina, Vicecomodoro Ángel de la Paz Aragonés Airport The National Rail station code for a railway station in London, England, Shadwell railway station An expressway in Johor, Malaysia, Senai–Desaru Expressway