# Geometry Vocab - Set 3

## 19 terms · Vocabulary related to triangles, quadrilaterals and polygons

### Triangle

a closed plane figure formed by three line segments joining three noncollinear points

### Exterior angle of a triangle

formed when one side of a triangle is extended

### Scalene triangle

triangle with no congruent sides

### Isosceles triangle

triangle with two congruent sides

### Equilateral triangle

triangle with three congruent sides

### Acute triangle

triangle with three acute angles

### Obtuse triangle

triangle with one obtuse angle

### Right triangle

triangle with one right angle

polygon with four sides

### Trapezoid

quadrilateral with one pair of parallel sides

### Parallelogram

quadrilateral with two pairs of parallel and congruent sides

### Rectangle

a parallelogram with four right angles

### Rhombus

a parallelogram with four congruent sides

### Square

a rectangle with four congruent sides or a rhombus with four right angles

### Polygon

a closed figure made up of three or more line segments

### Convex Polygon

a polygon with no angles greater than 180 degrees;

### Concave Polygon

a polygon with at least one angle that is greater than 180 degrees

### Regular Polygon

polygon with all congruent sides and all congruent angles

### Diagonal of a polygon

a line segment joining two non-adjacent vertices of a polygon