IR(Series of Letters)

**IR** or **Ir** may refer to:

## Arts and entertainment

* Integrated resort, a euphemism for a casino in Singapore
* I.R. Baboon, a fictional character in the cartoon series *I Am Weasel*
* *Imperator: Rome*, a 2019 video game published by Paradox Interactive

* Iarnród Éireann (Irish Rail), the national passenger and freight railway system of the Republic of Ireland
* Israel Railways, the state-owned railway company of Israel

### Other businesses and organizations

* Ingersoll Rand (NYSE trading symbol IR)
* International Rectifier, a former manufacturer of power semiconductors
* Independent-Republican Party of Minnesota, former name of the Republican Party of Minnesota

## Finance

* Incidence rate (market research)
* Interest rate, or (when referring to an asset class) interest rate derivative
* Information ratio, when referring to risk-adjusted returns of a financial security
* Investor relations, a management responsibility in which companies disclose information for regulatory compliance and for bond/share-holders to make investment judgments

## Science and technology

### Biology and medicine

* Immediate-release, related to time release technology in pharmaceuticals
* Incidence Rate, in epidemiology
* Insulin receptor, a transmembrane receptor that is activated by insulin
* Insulin resistance, a pathological condition
* Interventional radiology and interventional radiologist, an independent medical specialty
* Inverted repeat, a sequence of nucleotides that is the reversed complement of another sequence further downstream

### Computing

* .ir, the Internet country code top-level domain for Iran
* Adobe ImageReady, a bitmap graphics editor shipped with Adobe Photoshop by Adobe Systems
* Image retention, the LCD and plasma display equivalent of screen burn
* Information retrieval, the science of searching for information in or as documents or databases
* Information revolution, one of the theoretical frameworks within which trends in current society can be conceptualized
* Institutional repository, a digital collection for preserving the intellectual output of an institution
* Institutional research, the collection, analysis, and reporting of institutional data
* Instruction register, part of a CPU's control unit
* Intermediate representation, a computer data structure
* Internal router

### Other uses in science and technology

* Ir (newspaper), Latvian weekly newspaper
* Infrared, a portion of the electromagnetic radiation spectrum
* Impulse response, an output function of a dynamic system presented with a brief input signal
* Insulation resistance, a measure of how well the insulation material is performing in an electric appliance
* Ionizing radiation
* Iridium, symbol Ir, a chemical element

## Other uses

* Imperial–royal – Title of institutions of the Austrian Empire
* Industrial relations, the relations between management and workers in industry
* Ingenieur, abbreviated as *ir.*, an engineer's degree awarded by technical universities in the Netherlands, Belgium, Indonesia, and Malaysia.
* Injured reserve list, a reserve list for professional teams to use if a player is injured and unable to play for an extended time
* International relations, in political science, the study of foreign affairs of and relations among states
* *International Relations* (journal), an academic journal
* International rules football a hybrid code of football
* Iran, by ISO country code
* Ir (cuneiform), a sign in cuneiform writing
* Ir language, also known as Ta'Oi language. spoken in parts of Laos and Vietnam
* Istro-Romanian language
* InterRegio, part of Swiss Federal Railways

## See also

* ℝ, the symbol of the set of real numbers in mathematics
* Inland Revenue Department (disambiguation), a government revenue service in several countries
* International Rescue (disambiguation)
* IRS (disambiguation)