ER

ER or Er may refer to:


 * Еmergency room, a department of a medical facility that specializes in the acute care of patients without any prior appointments
 * ER, the ISO 3166-1 alpha-2 code of the country of Eritrea
 * ER, the IATA code of Astar Air Cargo

People
 * Nie Er (1912–1935), Chinese composer
 * Er. Eswaran, Indian politician and entrepreneur from Tamil Nadu

In media:
 * ER (TV series), a 1994–2009 American medical drama television series
 * E/R, a 1984–1985 American television sitcom
 * Eesti Rahvusringhääling, an Estonian public broadcasting organization
 * Er, an album by Nils Petter Molvær
 * Chico Enterprise-Record, the daily newspaper of Chico, California

In natural science:
 * Erbium, a chemical element
 * Relative static permittivity, a concept in chemistry represented as $$\epsilon_r$$
 * Estrogen receptor, a type of protein molecule
 * Endoplasmic reticulum, a type of organelle in cell biology
 * ER fluid, or Electrorheological fluid
 * Equine Exertional Rhabdomyolysis, a syndrome that damages the muscle tissue in horses
 * ER model, or Erdős–Rényi model

Parts of language:
 * Er (Cyrillic), the eighteenth letter of the Cyrillic alphabet
 * Er, alternate spelling for Yer, a letter of the Cyrillic alphabet
 * The suffix -er, which is added to an adjective or adverb to describe a degree of comparison. (e.g. fast to faster)
 * The suffix -er, which is added to a verb to make it an Agent noun. (e.g. cut to cutter)
 * "er", a filler word
 * Entre Ríos, a Spanish abbreviation

In technology:
 * ER (Extended Range), a classification of missiles and aircraft that indicates an extended travel capability
 * Engineer, a profession that applies knowledge to develop solutions to meet economic and societal needs
 * Entity-relationship model, an abstract and conceptual representation of data
 * Error Resilience, an audio coding method used in MPEG-4 Part 3


 * Other uses
 * Er (Biblical name), in the Biblical Book of Genesis, the eldest son of Judah
 * Er., an abbreviation used in Hebrew for Erubin, the second tractate of Moed
 * Er, the subject of Plato's Myth of Er
 * Earned run, a term in the game of baseball that denotes any run for which the pitcher is held accountable
 * Evidential reasoning approach, a concept in Decision Theory
 * ER party, or Estonian Reform Party
 * Elizabeth Regina, an alternate name of Queen Elizabeth
 * Eduardus Rex, a Latin abbreviation for King Edward
 * Elizabeth Regina, a Latin abbreviation for Queen Elizabeth
 * E.R., abbreviation for English Reports, or nominate reports of judgments of the English Courts, 1220 to 1866
 * Èrs, an ancient people inhabiting parts of what are now Northern modern Armenia, Northeast Turkey, Southern Georgia, and Northwest Azerbaijan