#### geometry

Mathematical discipline that studies the relations between points, straight lines, curves, surfaces and volumes.

#### obtuse angle

Angle between 90° and 180°.

#### acute angle

Angle that is smaller than a right angle (less than 90°).

#### right angle

Angle formed by two lines or two perpendicular planes that measures 90°.

#### perpendicular

Symbol denoting that a straight line meets another at a right angle.

#### is not parallel to

Symbol denoting that two straight lines do not remain at a constant distance from one other.

#### is parallel to

Symbol denoting that two straight lines remain at a constant distance from one another.

#### minute

Symbol placed in superscript after a number that denotes degrees in sixtieths of a measure.

#### second

Symbol placed in superscript after a number that denotes degrees in sixtieths of a minute.

#### pi

Constant that represents the ratio of a circle’s circumference to its diameter; its value is approximately 3.1416.

#### degree

Symbol placed in superscript after a number to denote the opening of an angle or the length of an arc, or in front of an uppercase letter to identify a scale of measurement.