Mathematics. Dictionary

Radius · R

A line segment between any point of a circle or sphere and its center.

Range (statistics) · R

In descriptive statistics, the range of a set of data is the size or width of the narrowest interval which contains all the data. It is calculated as the difference between the largest and smallest values (also known as the sample maximum and minimum). It is expressed in the same units as the data. The range provides an indication of statistical dispersion. Robust measures of range include the interdecile range and the interquartile range.

Rate · R

A ratio comparing two quantities expressed in different units.

Ratio · R

The relative magnitudes of two quantities (usually expressed as a quotient).

Rational number · R

A number that can be expressed as the ratio of two integers.

Ray · R

A line extending indefinitely in one direction from a point.

Real number · R

The limit of a convergent sequence of rational numbers, whether the limit is a rational number such as 2, -5, or 2/7 or whether the limit is an irrational number such as the square root of two or the circumference of the circle whose radius is one.

Reciprocal · R

The number obtained by dividing 1 by another given number; the result of exchanging the numerator and the denominator of a fraction.

Rectangle · R

Any quadrilateral having opposing sides parallel and four right angles.

Reflex angle · R

An angle greater than 180 degrees but less than 360 degrees.

Remainder · R

The number left over after a simple subtraction

Rhombus · R

A parallelogram having all sides of equal length.

Right angle · R

Half of the angle formed by a single straight line, equivalent to 90 degrees.

Right triangle · R

A triangle having a right angle as one of its interior angles.

Root · R

Of a number or expression, a number which, when raised to a specified power, yields the specified number or expression.

Ruler · R

A (usually rigid), flat, rectangular measuring or drawing device with graduations in units of measurement; a straightedge with markings.