# ER

ER or Er may refer to:

## 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 / EVIIR), the royal cypher of Edward VII
** Edward Rex (ER / EVIIIR), the royal cypher of Edward VIII
** Elizabeth II Regina (EIIR), the royal cypher of Elizabeth II

### Fictional characters

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

## Arts, entertainment and media
### 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)
* Entre Ríos Railway in Argentina (reporting mark ER)
* Estonian Reform 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
### 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

* Eritrea (ISO 3166-2 two letter country code)
* 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