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Theorema Egregium
The Theorema Egregium, Latin for "remarkable theorem", is Gauss's 1827 result that a surface's Gaussian curvature is intrinsic, unchanged by any bending that preserves distances within it.
Theoren Fleury
Theoren Fleury, known as Theo Fleury, is a Canadian former hockey right wing who played 15 NHL seasons, mostly with Calgary, and won the 1989 Stanley Cup.
Theoretical computer science
Theoretical computer science (TCS) is the branch of computer science studying the fundamental capabilities and limits of computation using mathematical methods, originating with Turing and Church in the 1930s.
Theoretical examination of the International Physics Olympiad
The theoretical examination of the International Physics Olympiad is a five-hour written test of three problems worth 30 of 50 marks, held on a separate day from the experimental exam.
Theoretical physics
Theoretical physics is the branch of physics that describes natural processes through mathematical models, explaining existing observations and making predictions that guide new experiments, from particle physics to condensed matter.
Theoretical sampling
Theoretical sampling is a qualitative research sampling method in which the emerging theory determines which data are collected next, developed by Glaser and Strauss in 1967.
Theoretical saturation
Theoretical saturation is the point in grounded theory research at which further data collection reveals no new theoretical insights, introduced by Barney Glaser and Anselm Strauss in 1967.
Theoretical yield
Theoretical yield is the maximum amount of product a chemical reaction can produce, calculated from the stoichiometry of the balanced equation and the limiting reactant.
Theories of humor
Theories of humor: superiority, relief, and incongruity accounts, plus benign violation theory, explaining what makes things funny, from Hobbes and Freud to McGraw and Warren.
Theories of truth
Theories of truth are philosophical accounts of what it is for a proposition or belief to be true, including the correspondence, coherence, pragmatic, semantic, and deflationary theories.
Theory
A scientific theory is a well-substantiated explanation of some aspect of the natural world that has survived repeated testing; theories explain laws but never become laws.
Theory of a Deadman
Theory of a Deadman (also shortened to Theory) is a Canadian rock band from Delta, British Columbia, formed in 2001, signed by Chad Kroeger to 604 Records, known for post-grunge hits like Bad Girlfriend and the 2026 EP Part 1: Funeral Songs.
Theory of change
A theory of change (ToC) is a planning and evaluation method that maps the causal pathways by which an intervention's activities are expected to produce its desired long-term outcomes.
Theory of computation
The theory of computation, also called computation theory, is the branch of computer science and mathematics that studies what problems machines can solve in principle and at what cost.
Theory of constraints
The theory of constraints, also known as constraints management, is a management philosophy developed by Eliyahu M. Goldratt that holds every system is limited by a few constraints.
Theory of everything
A theory of everything, sometimes called a final theory or superunification, is a hypothesized ultimate framework of physics unifying all four fundamental forces, with string theory its most studied candidate.
Theory of forms
The theory of forms, known as Platonic realism, is Plato's doctrine that eternal, unchanging Forms such as the Good are the true objects of knowledge, set out in dialogues like the Phaedo and Republic.
Theory of Games and Economic Behavior
Theory of Games and Economic Behavior is a 1944 book by John von Neumann and Oskar Morgenstern, published by Princeton University Press, that helped establish modern game theory.
Theory of Heat
Theory of Heat is the history of physics' explanations of heat, from the caloric fluid theory to thermodynamics and the kinetic theory identifying heat with molecular motion.
Theory of mind
Theory of mind (ToM), or mentalizing, is the capacity to attribute beliefs, desires, and intentions to others. Covers false belief tasks, neural systems, development, autism debates, and LLM evaluation.
Theory of multiple intelligences
Howard Gardner's 1983 theory of multiple intelligences holds that intelligence comprises seven or more relatively independent capacities, from linguistic to interpersonal; mainstream psychometrics instead supports a general factor g.
Theory of Official Nationality
The Theory of Official Nationality (Теория официальной народности) was the state doctrine of the Russian Empire under Nicholas I, built on Count Sergei Uvarov's 1833 formula "Orthodoxy, Autocracy, Nationality."
Theory of planned behavior
Theory of planned behavior (TPB), Icek Ajzen's 1985/1991 social psychology model: intention, driven by attitude, subjective norm, and perceived behavioral control, predicts behavior; distinguished from the theory of reasoned action by the perceived-control construct.
Theory of Prose
Theory of Prose (О теории прозы) is a 1925 collection of essays by the Russian literary theorist Viktor Shklovsky that sets out the Russian Formalist school's principles.
Theory of reasoned action
Theory of reasoned action (TRA), Fishbein and Ajzen's 1967/1975 model: behavior is predicted by intention, which is formed by attitude toward the behavior and subjective norm; extended by Ajzen's theory of planned behavior adding perceived behavioral control.
Theory of relativity
The theory of relativity is the pair of physical theories by Albert Einstein: special relativity (1905), covering space, time, and motion, and general relativity (1915).
Theory of the Earth
Theory of the Earth is James Hutton's 1788 geological work arguing that internal heat drives an endless cycle of erosion, deposition, and uplift over immense time.
Theory of the firm
The theory of the firm is the branch of microeconomics asking why firms exist and what determines their boundaries, beginning with Ronald Coase's 1937 article.
Theory of the Primary Stage of Socialism
The Theory of the Primary Stage of Socialism (社会主义初级阶段理论) is the official Chinese Communist Party doctrine that China remains in a long initial phase of socialism, first stated in 1981.
Theory of the second best
The theory of the second best is a 1956 result in welfare economics by Lipsey and Lancaster: if one optimality condition is blocked, the others may no longer hold.