# Geometry Vocabulary

## 40 terms · Geometry-related vocabulary from the Saxon Algebra 1 book.

A polygon with four sides

### Parallelogram

A quadrilateral that has two pairs of parallel sides

### Trapezoid

A quadrilateral that has exactly two parallel sides

### Rectangle

A parallelogram with four right angles

### Rhombus

An equilateral parallelogram

### Square

A rhombus with four right angles
or
A parallelogram that is equilateral and equiangular

### Perpendicular

Two lines that make a square corner at the point of intersection (90⁰)

### Point of Intersection

The point where two lines cross.

### Right Angle

The angle made by perpendicular lines (90⁰)

### Straight Angle

Two right angles form a straight angle (180⁰)

### Acute Angle

An angle that is smaller than a right angle (<90⁰)

### Obtuse Anlge

An angle that is larger than a right angle and smaller than a straight angle (between 90⁰ and 180⁰)

### Vertex

The endpoint of each segment in a polygon (a corner)

3-sided polygon

4-sided polygon

5-sided polygon

6-sided polygon

7-sided polygon

8-sided polygon

9-sided polygon

10-sided polygon

11-sided polygon

12-sided polygon

### Concave Polygon

A polygon with an indentation (has an interior angle >180⁰)

### Convex Polygon

Any polygon that does not have an indentation (all interior angles are <180⁰).

### Equilateral Polygon

A polygon with all equal sides

### Equiangular Polygon

A polygon with all equal angle measures

### Regular Polygon

A polygon that is equilateral and equiangular

### Right Triangle

A triangle that has one right angle

### Acute Triangle

A triangle with three acute angles

### Obtuse Triangle

A triangle with one obtuse angle

### Equiangular Triangle

A triangle where all of the angles have the same measure of 60⁰.

### Isosceles Triangle

A triangle that has at least two sides of equal length

### Scalene Triangle

A triangle where all three sides have different measures

### Equilateral Triangle

A triangle where all three sides have the same length

### Perimeter

The distance around a geometric object (measured in units)

The distance from the center of a circle to any point on the circle.

### Diameter

The radius of a circle times two

### Circumference

The perimeter of a circle (C=2πr)

### pi (π)

The exact number of times the diameter of a circle will go around the circle. Pi is an irrational number, but sometimes we use the approximation 3.14.