
Radical  a root sign 

Radius  Half the diameter of a circle. The distance between the middle of a circle and the circles surface. 

Random Number  A number choosed without definite aim, reason, or pattern. 

Ratio  The number or degree of one class of things in relation to another, or between one thing and another, expressed as a proportion . Example: In a car, the ratio of tires to steering wheel is 4 to 1, often wriiten 4:1. 

Ray  a line having one endpoint 

Real Number  any number that is not imaginary Example: "1.23156..., 5, 8/6, e, square root (3)" 

Reciprocal  Expressions, relations, or fractions that are opposite. Example: 1/2 is the reciprocal of 2/1 

Rectangle  A parallelogram with four right angles. 

Rectangular Prism  A prism in the shape of a rectangle. 

Regular Polygon  a polygon with all sides equal and all interior angles congruent 

Remainder  The portion of the dividend that is not evenly divisible by the divisor. 

Rhombus  An equilateral parallelogram with oblique angles. 

Right Angle  An angle that is 90 degrees. 

Right Triangle  A triangle with one of the angles equal to 90 degrees. 