ER

Er or ER may refer to:
 * Er (biblical figure), the eldest son of Judah
 * Er (Cyrillic), a letter in the Cyrillic alphabet
 * Er (Plato), the main character of the Myth of Er told by Plato in the Republic
 * ER (TV series), a popular NBC medical drama set primarily in an emergency room
 * E/R, a less successful 1980s sitcom also set in an emergency room and co-starring George Clooney on CBS
 * The concept of Elizabeth Regina, often appearing in official badges as a stylized "ER" (for example the badge of the Ministry of Defence Police)
 * The suffix -er used in creating a comparative adjective or adverb (e.g., smaller)
 * The symbol for erbium, an element.
 * A filler word used in dialogue displaying uncertainty to say something

ER is also an acronym for: Eesti Raadio - Estonian Radio ER - The Public Service Radio organisation in Estonia see *ERR
 * The Evidential Reasoning (ER) approach, an approach for multiple criteria decision analysis (MCDA) under uncertainty

Biology

 * Endoplasmic reticulum, in cell biology
 * Estrogen receptor, in molecular biology
 * Equine Exertional Rhabdomyolysis, a syndrome that causes the degeneration of muscle tissue in horses

People

 * Elizabeth Regina, Latin for Queen Elizabeth (plus other monarchs whose name begins with 'E' &mdash; latin for "king" is Rex)
 * Eleanor Roosevelt
 * Edgar Renteria, a baseball player

Misc

 * Emergency Room
 * Extended Range
 * The ISO country code for Eritrea
 * Entity-relationship model, a high-level conceptual data model
 * The IATA code for Astar Air Cargo
 * Oorah
 * The Chico Enterprise-Record, a daily newspaper of Chico, California
 * Relative permittivity may be represented as $$\epsilon_r$$
 * An earned run in baseball.

ER ER Er ER ER ER ER Er ER ER ER ER (Watt ėßß datt?) ER ER ER ER