# C1

C1, C01, C.I or C-1 may refer to:

## Arts and media

* C1, a note-octave in music
* C1 Television, a Mongolian television channel
* Cinema One, Philippine pay TV channel
* Schecter C-1 Hellraiser FR, a guitar model
* A Yamaha grand piano model
* "C1", a slang expression in the video game Counter-Strike, used to express agreement

## Biology and medicine
### Anatomy

* Cervical vertebra 1, the first cervical vertebrae of the vertebral column
* Cervical spinal nerve 1, a spinal nerve of the cervical segment

### Biochemistry

* C1 complex, the first component of the classical complement pathway
* C1 domain, an important secondary messenger protein domain
* C1-inhibitor, a human serine protease inhibitor
* C1 regulatory sequence for the insulin gene
* Apolipoprotein C1, a human lipoprotein
* Chlorophyll c1, a form of chlorophyll
* Cytochrome C1, a precursor protein to Cytochrome C
* Proanthocyanidin C1, a type of polyphenolic compound
* Prostaglandin C1, a form of prostaglandins

### Other uses in biology and medicine

* C1 and P1 (neuroscience), a component of the visual evoked potential
* ATC code C01, a subgroup of the Anatomical Therapeutic Chemical Classification System
* C01, the ICD-10 code for "malignant neoplasm of base of tongue", a form of oral cancer
* C1, the short name for a microfluidic single-cell analysis system sold by Fluidigm

## Chemistry

* C1 Chemistry, study of methane, methanol, carbon monoxide, carbon dioxide

## Computing
### Hardware

* C-One, a single-board microcomputer
* C1 NES TV, a family of Nintendo-television-set hybrids manufactured by Sharp Corporation in 1983
* ATI C1, codename of the Xbox 360 GPU Xenos
* Apple C1, a cellular modem chip

### Other uses in computing

* C0 and C1 control codes defined in ISO 6429
* C1 (protocol), a 1984 protocol for file transfer, also known as "Punter"
* TCSEC C1 security class
* A CPU power state in the Advanced Configuration and Power Interface

## Mathematics

* $C^{1}$, the set of all continuously differentiable functions
* C1 field, a quasi-algebraically closed field
* C1, the first of four pure modules taken in the Advanced Level (UK) Maths syllabus

## Transportation
### Air

* C-1 Trader, a cargo-version of the S-2 Tracker anti-submarine warfare aircraft of the United States Navy
* AEG C.I, a German World War I reconnaissance aircraft
* AGO C.I, a 1915 German reconnaissance biplane
* Albatros C.I, a 1915 German two-seat general-purpose biplane
* Aviatik C.I, a 1915 German observation plane
* Cierva C.1, a 1920 Spanish experimental autogyro
* DFW C.I, a WWI German reconnaissance aircraft
* Douglas C-1, a cargo/transport airplane produced by Douglas Aircraft for the U.S. Army Air Service starting in 1925
* Fokker C.I, a 1918 German reconnaissance biplane
* Friedrichshafen C.I, a 1914 German single-engined amphibious reconnaissance biplane
* Hansa-Brandenburg C.I, a 1916 German 2-seater armed single-engine reconnaissance biplane
* Kawasaki C-1, an indigenous transport aircraft of the Japanese Air Self-Defense Forces
* Otto C.I, a 1915 German reconnaissance biplane
* Rumpler C.I, a 1915 German two-seater single-engine reconnaissance biplane
* Southern Cross Airport (New Jersey) (FAA LID: C01)

### Land
#### Routes

* Circumferential Road 1 or C-1, an arterial road of Manila, Philippines
* London Buses route C1
* Route C1 (Shuto Expressway), the Inner Loop of Tokyo's Shuto Expressway system
* Claro M. Recto Avenue, a road in Metro Manila, Philippines
* Massachusetts State Route C1

#### Land vehicles

* BMW C1, a cabin scooter
* Chevrolet Corvette C1, first generation sold from 1953 to 1962, denoted a solid-axle rear-end
* Citroën C1, a small car
* Ford C1 platform, the Ford Motor Company's global compact car automobile platform
* Leapmotor C01, a battery electric executive sedan
* Lit C-1, a prototype cabin motorcycle
* Nimrod NRA/C1, a 1981 test design racing car
* Sauber C1, a Sauber sport car

#### Other uses in land transport

* C-1, the numberplate of the Prime Minister of Australia's official VIP transportation
* A type of heavy goods vehicle licence
* A one-way traffic sign in the Vienna Convention on Road Signs and Signals

### Rail

* Bavarian C I, an 1847 German steam locomotives class
* GNR Class C1 (small boiler), a British 4-4-2 steam locomotive class (classified C2 during LNER ownership)
* GNR Class C1 (large boiler), a British 4-4-2 steam locomotive class
* LB&SCR C1 class, an 1882 British freight steam locomotive
* Long Island Rail Road C1, a bilevel railcar built by Tokyu Car Corporation
* NER Class C1, a British 0-6-0 steam locomotive class
* PRR C1, an American PRR steam locomotive
* Finnish Steam Locomotive Class C1

### Sea

* HMS C1, a C-class submarine of the Royal Navy
* USS C-1 (SS-9), a C-class submarine of the United States Navy
* USS Newark (C-1), a protected cruiser of the United States Navy
* Type C1 ship, a small cargo vessel built by the United States in large numbers before and during World War II
* Isaac Peral (C-1), a Spanish submarine

### Space

* Cluster 1, also known as Rumba, an ESA satellite

## Sports

* C1, a solo canoe discipline including sprint canoe and canoe slalom
* C1 (classification), a para-cycling classification
* C1, an abbreviation for Class One offshore powerboat racing
* 'C1', the top category in Group C sportscar racing, used between 1985 and 1990
* C1, the UEFA Champions League (formerly known as the European Cup) in football
** Serie C1, the third highest football league in Italy until 2008

## Other uses

* C1, an international standard paper size defined in ISO 216 (648×917 mm)
* Bills C-1 and S-1, a pro forma bill normally introduced at the start of a parliamentary session in the Canadian House of Commons
* C1, also known as Vlakplaas, a unit of the South African Police responsible for assassinating opponents of Apartheid during the 1980s
* C1, a level in the Common European Framework of Reference for Languages
* C1, the use class for hotels, in town and country planning in the United Kingdom
* C1, a NRS social grade in the United Kingdom for the lower middle class
* a 2001 1.3 megapixels Olympus digital camera model
* a class of FM radio broadcasting in North America
* C1 pylon, a type of high voltage pylon
* Caldwell 1 (NGC 188), an open cluster in Cepheus
* C-1 visa, a type of visa for individuals transiting through the United States
* C1 Espresso, café in Christchurch, New Zealand
* Capital One, an American banking company