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 * Schecter C-1 Hellraiser FR, a guitar model * A List of Yamaha products#Acoustic musical instruments, 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#Products, 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 (graphics chip), Xenos

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 Major roads in Metro Manila, 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 * 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 * GNR Class C1 (large boiler), a British 4-4-2 steam locomotive * LB&SCR C1 class, an 1882 British freight steam locomotive * C1 (railcar), Long Island Rail Road C1, a bilevel railcar built by Tokyu Car Corporation * NER Class C1, a British 0-6-0 steam locomotive * PRR C1, an American PRR steam locomotive * Finnish Steam Locomotive Class C1

Sea

* , a C-class submarine of the Royal Navy * , a C-class submarine of the United States Navy * , 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 II (spacecraft)#Mission overview, 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 List of Olympus products#Digital cameras, Olympus digital camera model * a List of North American broadcast station classes#FM, 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