In this article, we share a comprehensive list of math words that start with the letter “R” to enhance your mathematical vocabulary.

**Radius-**Distance from the center of a circle to any point on its circumference.**Range-**Difference between the highest and lowest values in a data set.**Ratio-**Relationship between two numbers indicating how many times the first number contains the second.**Rational Numbers-**Numbers that can be expressed as a fraction of two integers.**Real Numbers-**All numbers on the number line, including both rational and irrational numbers.**Reciprocal-**The multiplicative inverse of a number.**Rectangle-**A quadrilateral with four right angles.**Reflection-**A transformation producing a mirror image of a figure.**Regression-**A statistical process for estimating relationships among variables.**Regular Polygon-**A polygon with all sides and angles equal.**Remainder-**The amount left over after division.**Root-**The solution of an equation expressed as an integer, fraction, or other mathematical expression.**Rhombus-**A quadrilateral with all four sides of equal length.**Right Angle-**An angle of 90 degrees.**Right Triangle-**A triangle with one right angle.**Rotation-**A circular movement of an object around a center or point.**Round-**To approximate a number to the nearest whole number, tenth, hundredth, etc.**Resultant-**The vector sum of two or more vectors.**Repetend-**The repeating part of a decimal.**Residual-**The difference between observed and predicted values in a regression analysis.**Resolution-**The smallest measurable interval in a mathematical context.**Reticence-**The quality of being reserved, not typically a mathematical term.**Reduced-**Simplified form of a fraction.**Radius of Convergence-**The radius within which a power series converges.**Rationalize-**To eliminate a radical from the denominator of a fraction.**Real Part-**The non-imaginary part of a complex number.**Reflex Angle-**An angle greater than 180 degrees but less than 360 degrees.**Row-**A horizontal group of values in a matrix or table.**Rational Function-**A function defined by the ratio of two polynomials.**Rounding Error-**The difference between the calculated approximation of a number and its exact mathematical value.**Rejection Region-**The set of values for which a null hypothesis is rejected in statistics.**Radical-**Another term for a root, especially square root.

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