SD may refer to:

Military and weaponry

  • Smith & Wesson SD, a line of pistol (first made 2010)
  • SD radar, an early US Navy radar system
  • Southern Cross Decoration (SD), a South African military award

Organisations

Political parties

  • Democratic Left (Italy) (2007–2010; )
  • Social Democrats (Slovenia) (founded 1993)
  • Solidarity (Brazil) (founded 2012)
  • Democratic Party (Poland) (founded 1937; )
  • Sweden Democrats (founded 1988)
  • Swiss Democrats, Switzerland (renamed 1990; )
  • Serbian Right (founded 2018; )

Other organisations

  • Sicherheitsdienst, Nazi intelligence service (1931–1945)
  • Sisters of the Destitute, a Syro-Malabar Catholic order (founded 1927)
  • Sudan Airways (founded 1946; IATA:<code>SD</code>)

Places

  • Sudan (ISO 3166 country code:<code>SD</code>)
  • A common abbreviation for the U.S. city of San Diego, California and the San Diego Padres—the city's Major League Baseball team
  • Shandong, a province of China
  • South Dakota, a US state
  • Eswatini (formerly Swaziland; SD on vehicle plates)

Science and technology

Astronomy

  • Subdwarf, a class of star
  • Surface detector, of cosmic rays at the Pierre Auger Observatory

Electronics and computing

  • SD card (Secure Digital), a flash memory card format
  • Software Distributor, an HP-UX system
  • Standard-definition television
  • Super Density Disc, an optical disc format
  • Stable Diffusion, a text-to-image generator

Mathematics

  • sd (elliptic function), one of Jacobi's elliptic functions
  • Standard deviation (SD), a statistical measure of variation

Medicine

  • Spasmodic dysphonia, a voice disorder
  • Stable disease, a RECIST chemotherapy outcome

Other uses in science and technology

  • Segregation distorter, a selfish genetic element which biases its own genetic transmission
  • Service design, holistic design of service experience
  • Spiral Dynamics, a model of individual and societal development
  • Storm Data, a US meteorological journal
  • System dynamics, of nonlinear systems

Other uses

  • Sekolah Dasar, term for primary school in Indonesia
  • Super D (cycling), a class of mountain bike race
  • Super deformed, an art style
  • Sindhi language (ISO 639-1 code: sd)
  • sine die, Latin, undated (literally without a day)

See also

  • SD1 (disambiguation)