S2

• S2 (star), Milky Way galaxy
• S/2007 S 2, a natural satellite of Saturn
• S2 impact (ie, "Spherules 2"), major impact of early Earth
• S2 map projection, a map projection created at Google
• S2 steel (shock resisting steel)
• S2: Keep out of the reach of children, a safety phrase in chemistry
• Disulfur (S₂), an allotrope of sulfur
• Sulfide (S²⁻) anion

Mathematics

• S², the two-dimensional n-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

Cars

• AS S2, a 1927 car manufactured in Poland
• 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 second stage of the Saturn V rocket

Rail

Locomotives

• Alco S-2, a locomotive
• Pennsylvania Railroad class 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)
• Line S2 (Nanjing Metro), a suburban rapid transit line currently under construction in China
• Line S2 (Wenzhou Rail Transit), a suburban rapid transit line currently under construction in China
• FGC line S2, a suburban train service in Barcelona Province

• 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

• 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

• 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

• Seremban 2, a suburb of Seremban, located in Negeri Sembilan, Malaysia
• 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