Registered report
A registered report is a journal-article format in which a study's rationale, design, and analysis plan are peer reviewed and accepted in principle before data are collected, guaranteeing publication regardless of results.
Regolith
Regolith is the layer of loose, fragmented rock material that overlies bedrock, formed by weathering, erosion, transport, or deposition, covering Earth, the Moon, and Mars.
Regorafenib
Regorafenib (brand name Stivarga) is an oral multikinase inhibitor developed by Bayer and approved in the United States in 2012 for metastatic colorectal cancer, advanced GIST, and hepatocellular carcinoma.
Regress argument (epistemology)
The regress argument, or epistemic regress, is a problem in epistemology holding that every chain of justifying reasons must end in basic beliefs, circle, or continue forever.
Regression analysis
Regression analysis, also known as statistical regression, is a set of statistical methods for estimating the relationship between a dependent variable and one or more predictors.
Regression calibration
Regression calibration is a statistical method for correcting bias from measurement error in a covariate, replacing it with its conditional expectation given the observed data before running the usual regression analysis.
Regression discontinuity design
The regression discontinuity design (RDD), introduced by Thistlethwaite and Campbell in 1960, estimates causal effects by comparing units just above and below a treatment cutoff.
Regression estimator (survey sampling)
The regression estimator, including the generalized regression (GREG) estimator, is a survey sampling estimator of a population total that improves precision by using known auxiliary totals.
Regression kriging
Regression kriging, also called residual kriging, is a hybrid spatial prediction method that fits a regression on covariates and kriges the residuals, widely used in digital soil mapping.
Regression toward the mean
Regression toward the mean, also called reversion to the mean, is the statistical phenomenon in which an extreme measurement is followed, on average, by a less extreme one.
Regression tree
A regression tree is a statistical and machine-learning method that predicts a continuous outcome by recursively partitioning data into regions and predicting the mean response in each region.
Regula falsi
Regula falsi, also called the method of false position, is a bracketing root-finding algorithm that uses the secant line through two points straddling a root.
Regular cardinal
A regular cardinal is an infinite cardinal whose cofinality equals itself, meaning it cannot be written as a union of fewer smaller sets; others are singular.
Regular chain (algebra)
In computer algebra, a regular chain is a triangular set of polynomials whose leading coefficients are regular modulo the saturated ideal of earlier polynomials, introduced by Kalkbrener in 1991.
Regular dodecahedron
The regular dodecahedron, also called the pentagonal dodecahedron, is one of the five Platonic solids, with 12 pentagonal faces, 30 edges, and 20 vertices; its dual is the icosahedron.
Regular graph
A regular graph is a simple, undirected graph in which every vertex has the same number of neighbors, its degree k; a k-regular graph exists exactly when nk is even.
Regular icosahedron
The regular icosahedron, or gyroelongated pentagonal bipyramid, is one of the five Platonic solids, a convex polyhedron with 20 equilateral triangular faces, 30 edges, and 12 vertices, with five faces meeting at each vertex.
Regular language
A regular language, also called a rational language, is a set of strings recognizable by a finite automaton, the lowest level of the Chomsky hierarchy.
Regular local ring
A regular local ring is a commutative Noetherian local ring whose maximal ideal can be generated by as many elements as its Krull dimension, making it algebraically smooth.
Regular matroid
A regular matroid is a matroid representable by a totally unimodular matrix, one whose subdeterminants are all 0, 1, or −1, making it representable over every field.
Regular octahedron
The regular octahedron is one of the five Platonic solids, with eight equilateral triangular faces, six vertices, and twelve edges, and the cube as its dual.
Regular polygon
A regular polygon, also called a regular 2-polytope, is a plane polygon with all sides and all interior angles equal, one existing for every side count from 3 up.
Regular semigroup
A regular semigroup is a semigroup in which every element a has an inverse b satisfying a = aba, including groups, inverse semigroups, and matrix semigroups.
Regular sequence
A regular sequence is a sequence of ring elements where each is a nonzerodivisor on the module left by the earlier ones, used to define depth.
Regular solution theory
Regular solution theory is a thermodynamic model of mixtures in which molecules mix randomly but the enthalpy of mixing is nonzero, introduced by Joel H. Hildebrand in 1927.
Regular space
In topology, a regular space is one where each point and closed set not containing it lie in disjoint open sets, a separation axiom between Hausdorff and normality.
Regular tetrahedron
A regular tetrahedron is the simplest of the five Platonic solids, with four equilateral triangular faces, four vertices, and six edges, described by the Schläfli symbol {3,3}.
Regular variation
Regular variation is a property of measurable functions describing power-law asymptotic behavior, introduced by Jovan Karamata in 1930 and standard in probability and extreme value theory.
Regularization (mathematics)
Regularization in mathematics is the construction of stable approximate solutions to ill-posed problems by adding constraints, introduced by Tikhonov in 1963 and central to ridge regression and the lasso.
Regularized regression
Regularized regression adds a penalty term to least-squares fitting, shrinking coefficients toward zero to lower prediction error; ridge and the lasso are the canonical cases.