All articles starting with R
22,461 articles
Ration card (India)
A ration card in India is a state-issued document letting households buy subsidized rice and wheat from fair price shops under the Public Distribution System.
Rational choice model
Rational choice model (rational choice theory): formal social-science framework modeling choice as axiomatic utility maximization, foundational to neoclassical microeconomics, critiqued by bounded rationality and behavioral economics.
Rational emotive behavior therapy
Rational emotive behavior therapy (REBT), created by Albert Ellis in 1955, is the pioneering cognitive behavior therapy using the ABC model of activating events, irrational beliefs, and consequences, renamed REBT in 1993.
Rational expectations
Rational expectations, also called the rational expectations hypothesis, is an economic theory proposed by John Muth in 1961 and applied to macroeconomics by Robert Lucas in 1972.
Rational function
A rational function, also called a fractional-rational function, is a function expressible as the ratio of two polynomials; such ratios form the field of rational functions F(x) in abstract algebra.
Rational ignorance
Rational ignorance, from Anthony Downs's 1957 An Economic Theory of Democracy: voters stay uninformed because information costs exceed the negligible benefit of a non-decisive vote; studied via cue-taking, motivated ignorance, and electoral models.
Rational interpolation
Rational interpolation approximates a function by a ratio of two polynomials forced through given data points, preferred over a single polynomial when the function has poles or nearly singular behavior.
Rational irrationality
Rational irrationality, coined by economist Bryan Caplan (Eastern Economic Journal 2000; Kyklos 2001), explains systematically biased, high-certitude political and religious beliefs as privately cheap consumption of pleasing false beliefs, extending rational ignorance and expressive voting.
Rational mapping
A rational mapping, or rational map, in algebraic geometry is a map between algebraic varieties given by rational functions, defined away from a closed subset.
Rational method (hydrology)
The rational method is an empirical hydrology formula, developed by Thomas Mulvany in 1850, that estimates peak runoff as the product of drainage area, runoff coefficient, and rainfall intensity.
Rational number
A rational number is a number that can be written as a fraction p/q of two integers, with q not zero; every integer and every terminating or repeating decimal is one.
Rational point
A rational point is a solution of an algebraic variety's defining equations whose coordinates are all rational numbers; finding them is the central problem of arithmetic geometry.
Rational reconstruction
Rational reconstruction is a computer algebra problem: recovering the rational number n/d from its residue a modulo m under size bounds, first solved by Paul S. Wang in 1981.
Rational representation
A rational representation of an algebraic group G is a linear representation on a finite-dimensional vector space given by a regular homomorphism G → GL(V).
Rational root theorem
The rational root theorem states that any rational root p/q of a polynomial with integer coefficients has p dividing the constant term and q dividing the leading coefficient.
Rational Software
Rational Software was an American software development tools company co-founded in 1981 by Paul Levy and Michael Devlin, acquired by IBM in 2003 for about $2.1 billion.
Rational surface
A rational surface is a two-dimensional algebraic variety defined over an algebraically closed field and birationally isomorphic to the projective plane, the simplest class in the Enriques–Kodaira classification of algebraic surfaces.
Rationale for the 2026 Iran war
Rationale for the 2026 Iran war: the US and Israeli justifications for Operation Epic Fury, launched February 28, 2026, targeting Iran's missiles, navy, proxies, and nuclear program, and the intelligence, legal, and diplomatic disputes over those aims.
Rationale for the Iraq War
Rationale for the Iraq War: the US and UK justifications for the March 2003 invasion, chiefly Iraqi WMD, terrorism links, and democratization; later inquiries found the intelligence flawed and no stockpiles existed.
Rationalism
Rationalism, or epistemological rationalism, is the philosophical view that some knowledge comes from reason alone, independent of sense experience, classically represented by Descartes, Spinoza, and Leibniz.
Rationalist community
Rationalist community, also rationality community or rationalsphere: social movement formed around Overcoming Bias and LessWrong (Eliezer Yudkowsky, Robin Hanson) from 2006-2009, centered on Bayesian reasoning, cognitive bias, and AI risk, overlapping with effective altruism.
Rationality
Rationality: the property of conforming to standards of good cognition, divided into epistemic rationality of belief and instrumental rationality of means to ends; includes Herbert Simon's 1957 bounded rationality, satisficing, and the rationality wars.
Rationalization (psychology)
Rationalization (psychology): an unconscious defense mechanism, named by Ernest Jones in 1908, in which plausible false reasons justify intolerable motives; linked to Festinger's cognitive dissonance theory and rated a disavowal-level defense in the DMRS hierarchy.
Rationing
Rationing is the allocation of a scarce good by a rule other than price, such as queues or coupons, when price is held below its market-clearing level.
Rationing in the United Kingdom
Rationing in the United Kingdom: British WWII and postwar controls on food, clothing, petrol, and furniture, from petrol rationing in 1939 and food rationing on 8 January 1940 to the end of meat rationing in July 1954.
Ratite
Ratite is a large flightless bird belonging to the paleognath lineage, derived from the Latin word ratis for its raft-like breastbone. It includes ostriches of Africa and emus of Australia.
Ratko Djukanović
Ratko Djukanović is a British-based respiratory physician who holds the Chair of Medicine at the University of Southampton and studies airway inflammation in asthma and COPD.
Ratko Mladić
Ratko Mladić, 'Butcher of Bosnia', Bosnian Serb VRS Main Staff commander (1992-1995) during the Sarajevo siege and Srebrenica genocide; convicted by the ICTY in 2017, life sentence upheld 2021, died in The Hague 27 August 2026.
Ratlam (रतलाम)
Ratlam (रतलाम) is a city and district in Malwa, Madhya Pradesh, formerly a Rathore Rajput princely state founded by Ratan Singh around 1650. Known for its 1829 new town, opium and salt trade, and GI-registered Ratlami Sev namkeen.
Ratlines (World War II)
The Ratlines, also called the Vatican Ratlines, were clandestine escape routes that helped Nazi war criminals flee Europe after World War II, chiefly through Spain and Italy to Argentina.