# E1

E1, E01, E.I or E-1 may refer to:

## Transportation
### Aircraft

* Azcárate E-1, a Mexican sesquiplane trainer
* Fokker E.I, a German fighter aircraft
* Grumman E-1 Tracer, an American airborne early warning aircraft
* Hydra Technologies E1 Gavilán, a hand-launched Mexican unmanned electronic surveillance drone
* Junkers E.I, the Idflieg designation for the 1916 Junkers J1 monoplane
* LVG E.I, a 1915 German two-seat monoplane
* NFW E.I, a 1917 German monoplane fighter
* Pfalz E.I, a Morane-Saulnier H monoplane built under licence for Germany
* Siemens-Schuckert E.I, a 1915 German single seat monoplane
* Standard E-1, a 1917 early American Army fighter aircraft

### Automobiles

* BMW E1, a 1991 and 1993 German electric/hybrid city car concept
* BYD e1, a 2019–present Chinese electric city car
* Dongfeng Fengguang E1, a 2019–present Chinese electric mini crossover
* Haima E1, a 2020–present Chinese electric city car
* Roewe E1, a 2012 Chinese electric city car concept later produced as the Roewe E50
* E1, a Mazda E type piston engine
* Switch E1, a bus Built by Switch Mobility
* Bestune E01, a compact electric crossover

### Submarines

* HMS E1, an E-class submarine of the Royal Navy
* USS E-1 (SS-24), a 1917 E-class submarine of the United States Navy

### Roads

* E01, Southern Expressway in Sri Lanka
* European route E01, from Northern Ireland to Spain
* E1 European long distance path, a long-distance hiking route from Norway to Italy
* London Buses route E1, a transport for London contracted bus route
* Tomei Expressway and Meishin Expressway, route E1 in Japan
* North–South Expressway Northern Route and New Klang Valley Expressway, route E1 in Malaysia
* E1 expressway (Philippines) (North Luzon Expressway, Subic–Clark–Tarlac Expressway, and Tarlac–Pangasinan–La Union Expressway), expressway route in the Philippines
* E1 expressway (Pakistan)

### Trains and locomotives

* E1 Series Shinkansen, a Japanese high-speed train
* Bavarian E I, a German steam engines locomotive model
* EMC E1, a diesel locomotive
* LB&SCR E1 class, an 1874 British 0-6-0 steam locomotive
* NCC Class E1, a Northern Counties Committee Irish steam locomotive
* NER Class E1, an 1898 class of small 0-6-0T steam locomotive
* PRR E1, an American PRR 4-4-2 steam locomotive
* SP&S Class E-1, a 1934 steam locomotives class

## Science and mathematics
### Biochemistry

* E1 (HCV), a viral structural protein found in hepatitis C
* E1, a unimolecular elimination mechanism in organic chemistry
* E1-enzymes, also known as Ubiquitin-activating enzymes, an enzyme which catalyzes the first step in the ubiquitination reaction, which targets a protein for degradation via a proteasome]
* E1 regulatory sequence for the insulin gene
* Estrone, a hormone
* Pyruvate dehydrogenase (E1), the first component enzyme of pyruvate dehydrogenase complex
* Acireductone synthase, an enzyme
* Haplogroup E1 (Y-DNA), a human Y-chromosome DNA haplogroup

### Mathematics

* Exponential integral, $E_{1}(z)=\int _{1}^{\infty }{\frac {e^{-tz}}{t}}\,{\rm {d}}t~$, mathematical function
* the E1 series (number series) of preferred numbers

### Medicine

* E1-isoprostane, a type of isoprostane

## Businesses and organizations

* E1 Music, an independent record label in the United States
* E1 Corp., a Korean chemical and oil company, member of the LS Group
* Entertainment One, an international media company

## Electronics

* Honda E1, a predecessor of the ASIMO humanoid robot
* Olympus E-1, a digital single-lens reflex camera

## Places

* E1 (Jerusalem), an area east of Jerusalem in the West Bank
* E1 postcode district, London, England, United Kingdom

## Other uses

* E01, ECO code for the closed variation of the Catalan Opening in chess
* E01, the Encase Image File Format
* E-1 (rank), the pay grade for enlisted ranks of Private, Airman Basic, and Seaman Recruit in the United States Military
* E1 grade, a difficulty level in rock climbing
* E-1 (rocket engine), a liquid propellant rocket engine
* E1 carrier, an E-carrier European telecommunications standard
* E1, an AMD CPU from the Bobcat (microarchitecture) family
* E1, abbreviation for the Oracle JD Edwards EnterpriseOne software
* E1 on Gardiner's sign list, representing the bull