S2 (St

S2 or S II may refer to:

Science and technology

* S2 (star), Milky Way galaxy
* S/2007 S 2, a natural satellite of Saturn
* Disulfur (S₂), an allotrope of sulfur
* S2: Keep out of the reach of children, a safety phrase in chemistry
* S2 steel (shock resisting steel)
* S2 map projection, a map projection created at Google

Mathematics

* S², the two-dimensional sphere
* S₂, the permutation group on two elements

Biology and medicine

* British NVC community S2, a swamps and tall-herb fens community in the British National Vegetation Classification system
* Schneider 2 cells, or S2 cells, a commonly used ''Drosophila'' cell line

* Secondary somatosensory cortex, a brain area in the parietal cortex
* Sacral spinal nerve 2, a spinal nerve of the sacral segment
* Schedule 2, an Australian legal category assigned to drugs; See Standard for the Uniform Scheduling of Medicines and Poisons
* S2, the second sacral vertebrae
* S₂ (heart sound), a sound in cardiac auscultation
* ATC code S02 ''Otologicals'', a subgroup of the Anatomical Therapeutic Chemical Classification System

Computing

* S2 (programming language)
* S2 Spreadsheet, by IBM in 1984

Transportation

Cars

* Audi S2, a turbo-charged sports car
* Lotus Elise S2, a Lotus Elise production series of roadster automobile
* Porsche 944 S2, a 3l naturally aspirated Porsche 944 sports car

Roads and bus routes

* County Route S2 (California)
* Expressway S2 (Poland), a southern bypass of Warsaw
* S2 National Highway, one of the National Highways of Pakistan
* S2 expressway (Shanghai), an expressway in Shanghai also known as the ''Hulu Expressway''
* S2, an abbreviation for a standard single carriageway road, with a single lane going in each direction
* Stagecoach Gold bus route S2, a bus route in Oxfordshire, England

Aviation and space

* Bangladesh (aircraft registration code)
* JetLite (IATA airline code)
* Focke-Wulf S 2, a 1928 German trainer aircraft
* Grumman S-2 Tracker, a 1952 United States Navy anti-submarine warfare (ASW) aircraft
* SABCA S-2, a 1926 Belgian aircraft
* Short S.2, a Short Brothers aircraft
* Strojnik S-2, motorglider
* S-II or S-2, the 2nd stage of the Saturn V rocket

Rail

Locomotives

* Alco S-2, a locomotive
* PRR S2, a unique steam turbine locomotive
* NER Class S2, a class of British steam locomotives

Passenger services

* S2 (Berlin), an S-Bahn service
* S2 (Dresden), an S-Bahn service
* S2 (Munich), an S-Bahn service
* S2 (Nuremberg), an S-Bahn service
* S2 (RER Vaud), an S-Bahn service in Switzerland
* S2 (Rhine-Main S-Bahn), an S-Bahn service
* S2 (Rhine-Ruhr S-Bahn), an S-Bahn service
* S2 (St. Gallen S-Bahn), an S-Bahn line in Switzerland
* S2, a planned Bremen S-Bahn service
* S2, a Hamburg S-Bahn service
* S2, a Hanover S-Bahn service
* S2, a RheinNeckar S-Bahn service
* S2, a Rostock S-Bahn service
* S2, a Stuttgart S-Bahn service
* S2, a Stadtbahn Karlsruhe service
* S2 (ZVV), a service of the S-Bahn Zürich in Switzerland
* Line S2 (BCR), a commuter rail service in Beijing
* Line S2 (Milan suburban railway service)
* FGC line S2, a suburban train service in Barcelona Province

Military

* Soviet submarine ''S-2'', a Soviet World War II submarine
* Grumman S-2 Tracker, a US Navy aircraft
* Finnish torpedo boat ''S2'', which sank in 1925
* USS ''S-2'' (SS-106), a US Navy submarine
* Göta Signal Corps (designation S2), a 1944–1997 Swedish Army signal unit
* S2 (missile), the first deployed French land-based strategic missile
* S-2, a military intelligence officer on the staff of a regiment or battalion
* HMS ''Rorqual'' (S02), a 1956 British Royal Navy ''Porpoise''-class submarine
* ORP S-2, Polish World War II motor gun boat

Organisations

* S2 Records, a subsidiary of Sony Music
* S2 (TV channel), a former Scottish television channel
* S2 Games, a video game developer
* S2 Yachts, a defunct sailboat-building company

Products

* Samsung Galaxy S II, an Android smartphone
* Samsung Gear S2, a Tizen smartwatch
* Samsung Galaxy Tab S2, an Android tablet

Cameras

* Nikon S2, a 35mm rangefinder camera produced between 1954 and 1958 as part of the Nikon S-mount range
* Nikon 1 S2, a digital mirrorless interchangeable lens camera
* Canon PowerShot S2 IS, a 2005 5.0 megapixel digital camera
* FinePix S2 Pro, a 2002 interchangeable lens digital single-lens reflex camera by Fuji
* Leica S2, a 2009 37 million pixel medium format digital single-lens reflex camera

Other uses

* S2, a version of the racing simulation ''Live for Speed''
* S2, a district of the S postcode area, covering areas of eastern Sheffield
* Seattle Sounders FC 2, nicknamed S2
* Second year, in the Scottish education system
* S2 (classification), used for categorising swimmers based on their level of disability
* ''Splatoon 2'', a 2017 video game for the Nintendo Switch
* Pitts Special, Two-Seat Aerobatics Biplane
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