ER

ER or Er may refer to:

Places

 * English Republic, alternative name for the Commonwealth of England
 * Eritrea (ISO 3166-2 two letter country code)

United States

 * East Rochester, New York
 * Erie, Pennsylvania

People

 * Er (biblical person), the eldest son of Judah in the biblical book of Genesis
 * Nie Er (1912–1935), Chinese composer
 * Elliot Rodger (July 24, 1991 – May 23, 2014), English-American incel mass shooter
 * A Royal cypher representing a monarch
 * Elizabeth Regina (ER), the royal cypher of Elizabeth I
 * Edward Rex (ER / E VII R), the royal cypher of Edward VII
 * Edward Rex (ER / E VIII R), the royal cypher of Edward VIII
 * Elizabeth II Regina (E II R), the royal cypher of Elizabeth II

Fictional characters

 * Er, a character in Plato's Myth of Er

Music

 * Er, an album by Nils Petter Molvær
 * "ER" (song), a 2012 single by Japanese boy band Kanjani Eight
 * "ER", a song by Royce da 5'9" featuring Kid Vishis from Success Is Certain

Periodicals

 * Chico Enterprise-Record, the daily newspaper of Chico, California

Television

 * ER (TV series), a 1994–2009 American television medical drama series
 * E/R, a 1984–1985 American television sitcom

Businesses and organizations

 * Astar Air Cargo (IATA designator ER)
 * Eastern Railway (India)
 * Eldorado Reno, a hotel and casino in Reno, Nevada
 * Eldorado Resorts, a gaming company located in Reno, Nevada
 * Entre Ríos Railway in Argentina (reporting mark ER)
 * Estonian Reform Party
 * United Russia, or Yedinaya Rossiya, a Russian political party

Finance and banking

 * ER, abbreviation of exchange rate
 * ER, abbreviation of expense ratio

Language

 * Er (Cyrillic) (Р / р), a letter of the Cyrillic alphabet corresponding to the Latin letter "R"
 * Er (cuneiform), a sign in cuneiform writing
 * "er", a filler word in English
 * Er, alternate spelling for Yer (Ъ / ъ), the hard-sign letter of the Cyrillic alphabet
 * Suffix -er
 * -er, a suffix added to adjectives or adverbs to form a comparative (e.g., fast to faster)
 * -er, a suffix added to a noun to indicate resident of, as in New Yorker
 * -er, a suffix added to a verb to make it an agent noun (e.g., cut to cutter)
 * Oxford "-er", a suffix used to form words like rugger and footer
 * Erhua (儿化), rhotacization of spoken syllables in Beijing dialect of Mandarin Chinese with the -er suffix (儿)

Science and technology

 * Erdős–Rényi model, a model in graph theory

Biology and medicine

 * Emergency room, or emergency department, in a medical facility
 * Endoplasmic reticulum, a type of organelle in cell biology
 * Er blood group system
 * Equine exertional rhabdomyolysis, a syndrome that damages muscle tissue in horses
 * Estrogen receptor, a type of protein molecule
 * Extraction ratio, a pharmacokinetic property

Chemistry and physics

 * $$\epsilon_r$$, a representation for relative static permittivity
 * Electrorheological (ER) fluid, a type of chemical suspension
 * Enantiomeric ratio, a concept in chemistry
 * Erbium, symbol Er, a chemical element
 * Einstein-Rosen bridge (ER) relativistic wormholes

Computing

 * .er, country code top-level domain (ccTLD) for Eritrea
 * Entity–relationship model, a conceptual representation of data
 * Error Resilience, an audio coding method used in MPEG-4 Part 3

Other uses

 * Er., Hebrew abbreviation for 'Eruvin, the second tractate of Moed
 * Earned run, a term in the game of baseball
 * Emergency Response, incident response team or emergency procedure related to emergency services
 * English Reports of the English Courts from 1220 to 1866