# S1

S1, S01, S.I, S-1, S.1, Š-1 or S 1 may refer to:

## Biology and chemistry

* S1 nuclease, an enzyme that digests singled-stranded DNA and RNA
* S1: Keep locked up, a safety phrase in chemistry
* Primary somatosensory cortex, also known as S1
* Tegafur/gimeracil/oteracil, also known as S-1, a chemotherapy medication

## Entertainment

* S1 (Indian TV channel), a Hindi-language channel
* S1 (Swiss TV channel), a German-language channel
* S1 (producer), a hip hop producer, member of the group Strange Fruit Project
* S1 No. 1 Style, a Japanese adult video company
* Gibson S-1, a guitar made by the Gibson Guitar Corporation
* A member of the S1W (group) that later became part of the music group Public Enemy.

## Government

* Bill S-1, a pro forma bill in Canadian Parliament
* Form S-1, a U.S. Securities and Exchange Commission filing
* S-1 Executive Committee, a United States government entity during World War II
* S1 (military), an administrative position within military units

## Technology

* ACPI S1 power state, in computing; see Advanced Configuration and Power Interface § Global states
* Apple S1, integrated computer used in the Apple Watch
* Canon PowerShot S1 IS, a 2004 3.2 megapixel digital camera
* FinePix S1 Pro, a 2000 interchangeable lens digital single-lens reflex camera by Fujifilm
* Nikon Coolpix S1, a digital camera
* S1 Corporation, an American software development company
* S1 Core, a microprocessor-core
* S1 MP3 Player
* Samsung Galaxy S (2010 smartphone)
* Sendo S1, a Sendo mobile phone model
* Siemens S1, a Siemens mobile phone
* Sony BDP-S1, a first generation Blu-ray Disc (BD) Player
* S1, an EPC in an LTE/4G network

## Transportation
### Routes
#### China

* Line S1 (Beijing Subway)
* Line S1 (Nanjing Metro)
* Line S1 (Wenzhou Rail Transit)
* S1 Yingbin Expressway in Shanghai

#### Germany

* S1 (Berlin), an S-Bahn line
* S1 (Dresden), an S-Bahn line
* S1 (Munich), an S-Bahn line
* S1 (Nuremberg), an S-Bahn line
* S1 (Rhine-Main S-Bahn), an S-Bahn line
* S1 (Rhine-Ruhr S-Bahn), an S-Bahn line
* S1 (Stuttgart), an S-Bahn line
* a planned Bremen S-Bahn line
* a Hamburg S-Bahn line
* a Hanover S-Bahn line
* a RheinNeckar S-Bahn line
* a Rostock S-Bahn line
* a Stadtbahn Karlsruhe line

#### Spain

* FGC line S1, a suburban train line in Barcelona Province
* S1a (Bologna metropolitan railway service)
* S1b (Bologna metropolitan railway service)

#### Switzerland

* S1 (Bern S-Bahn), an S-Bahn line in the canton of Bern
* S1 (RER Vaud), an S-Bahn line in the canton of Vaud
* S1 (St. Gallen S-Bahn), an S-Bahn line in the canton of St. Gallen
* S1 (ZVV), now subsumed by S24, a Zürich S-Bahn line

#### United States

* County Route S1 (California)
* S1 (Long Island bus)

#### Other countries

* S1 (Vienna), an S-Bahn line in Austria
* Line S1 (Milan suburban railway service), Italy
* S-1 Strategic Highway, Pakistan
* Expressway S1 (Poland)
* Stagecoach Gold bus route S1, in Oxfordshire, England, UK

### Vehicles
#### Aircraft

* Blackburn Buccaneer S.1 jet naval strike aircraft
* Focke-Wulf S 1, a German Focke-Wulf aircraft
* Fokker S.I, a 1919 Dutch primary trainer aircraft
* Hopfner S-1, a Hopfner aircraft
* Letov S-1, a 1920 Czechoslovak surveillance aircraft
* Loening S-1, a United States Army Air Service seaplane
* Loughead S-1 Sport 1920 US biplane
* Martinsyde S.1, a 1914 British biplane aircraft
* Pantsir-S1, a Russian anti-aircraft system
* Pitts S-1 aerobatic biplane
* S-1 Loening, a United States Army Air Service seaplane
* SSBS S1, a French experimental rocket
* Swift S-1, a 1991 Polish single seat aerobatic glider

#### Cars

* AS S1, a 1927 car manufactured in Poland
* Audi S1, performance variant of Audi A1
* Invicta S1, a 2004 sports car
* Leapmotor S01, an all-electric car
* S1 Scout Car, an armoured car built in Australia during the Second World War
* Superformance S1 Roadster, a Lotus Seven Type replicar produced in South Africa 2001–2004
* Saleen S1, an American sports car

#### Other vehicles

* Alco S-1, a locomotive
* PRR S1, a duplex locomotive developed by the Pennsylvania Railroad
* LNER Class S1, a class of British steam locomotives
* NER Class S1, a class of British steam locomotives
* USS S-1 (SS-105), a 1918 United States Navy experimental submarine

## Other uses

* S1 (classification), a disability swimming classification
* S postcode area covering Sheffield City Centre
* in human anatomy:
   * the first sacral vertebra
   * the sacral spinal nerve 1 of the vertebral column
   * the primary somatosensory cortex in the brain
* Senior 1, the First Year in the Scottish secondary education system
* Season (television) or series one
* Comet Ikeya-Seki, C/1965 S1
* Upplands regemente (signal), a 1902 Signal Regiment of the Swedish Armed Forces

## With superscripts and subscripts

S$_1$ may refer to :
* S1 (heart sound), a heart sound in cardiac auscultation
S$^1$ may refer to :
* S$^1$, the n-sphere in two dimensions i.e. a circle
* Inverse second (s$^{−1}$), a unit of frequency

## S01

S01 may refer to :
* Akai S01, an Akai synthesizer
* ATC code S01 Ophthalmologicals, a subgroup of the Anatomical Therapeutic Chemical Classification System
* HMS Porpoise (S01), a 1956 Porpoise-class submarine of the Royal Navy
* MULTI-S01, an encryption algorithm based on a pseudorandom number generator