# Introduction to Geometry - Figures

## 32 terms · Common Figures in Geometry

### line

defined as having infinite length, but no width or thickness

### line segment

part of a line with two endpoints

### ray

part of a line with one endpoint

### plane

a flat surface that continues forever

### bisector

a ray, line, line segment, or plane that intersects the segment at its midpoint, a line, ray, segment, or plane that intersects a segment at its midpoint

### polygon

A closed plane figure made up of line segments

### regular polygon

a polygon with all sides and all angles equal

### equilateral polygon

a polygon in which all sides are congruent

### concave polygon

a polygon with at least one diagonal outside the polygon

### square

a parallelogram with four congruent sides and four right angles

a polygon with four sides

### pentagon

a polygon with five sides

### hexagon

a polygon with six sides

### angle

formed by two rays that share a common endpoint

### triangle

a polygon with three sides

### isosceles triangle

a triangle with two equal sides

### scalene triangle

a triangle with no two sides of equal length

### right angle

A 90 degree angle

### obtuse triangle

a triangle with an obtuse angle

### acute triangle

a triangle with three acute angles

### right triangle

a triangle with one right angle

### kite

a quadrilateral with two pairs of congruent sides

### rhombus

a parallelogram with 4 congruent sides

### rectangle

A parallelogram with 4 right angles

### parallelogram

A quadrilateral with two pairs of parallel sides

### diagonal

a line segment connecting any two vertices of a polygon

### equilateral triangle

a triangle with three congruent sides

### acute angle

An angle less than 90 degrees

### obtuse angle

An angle more than 90 degrees

### convex polygon

a polygon in which each of its diagonals are inside the polygon

### Octagon

An eight sided polygon.

### Decagon

A ten sided polygon.