A fraction whose decimal representation contains a finite number of digits.

The product of zero and any number is zero.

The distance of a number from zero; the positive value of a number.

A positive angle measuring less than 90 degrees.

A triangle each of whose angles measures less than 90 degrees.

The number zero is called the additive identity because the sum of zero and any number is that number.

The additive inverse of any number x is the number that gives zero when added to x. The additive inverse of 5 is -5.

Two angles that share both a side and a vertex.

The union of two rays with a common endpoint, called the vertex.

A portion of the circumference of a circle.