# 8R Geometry

## 45 terms · Basic Geometry terms

### Alternate interior angles

Angles that lie within a pair of lines and on opposite side of a transversal. They are also congruent

### Complementary angles

two or more angles whose sum is 90 degrees

### corresponding angles

lie on the same side of the transversal and in corresponding positions

are a pair of angles with a common vertex and a common side, but no common interior points

### line

A series of points that extends in two opposite directions without end.

### Line segment

part of a line with two endpoints

### parallel lines

lines in a plane that never intersect

### perpendicular lines

Two lines that intersect to form right angles

### point

a location that has no size

### Supplementary angles

Two or more angles whose sum is 180 degrees

### vertex

The common endpoint of an angle

### Vertical angles

a pair of opposite congruent angles formed by intersecting lines

### Ray

(mathematics) a straight line extending from a point

### Right angle

an angle that measures 90 degrees

### Acute angle

an angle that measures less than 90 degrees but more than 0 degrees

### Obtuse angle

An angle that measures more than 90 degrees but less than 180 degrees

### straight angle

an angle of 180 degrees

### Congruent Angles

Angles that have the same measure

### Congruent Sides

sides that have the same length.

### Scalene Triangle

a triangle with no congruent sides

### Isosceles Triangle

a triangle with two equal sides

### Equilateral Triangle

a triangle with three congruent sides

### Right Triangle

a triangle with one right angle

### Acute Triangle

a triangle whose interior angles are all acute

### Obtuse Triangle

a triangle that contains an obtuse interior angle

a four-sided polygon

### pentagon

a five-sided polygon

### hexagon

a six-sided polygon

### octagon

an eight-sided polygon

### nonagon

a nine-sided polygon

### heptagon

a seven-sided polygon

### decagon

a polygon with 10 sides and 10 angles

### trapezoid

a quadrilateral with exactly one pair of parallel sides

### paralleogram

a quadrilateral with two pairs of parallel sides.

### Rhombus

a parallelogram with 4 congruent sides

### rectangle

a parallelogram with four right angles

### square

(geometry) a plane rectangle with four equal sides and four right angles

### Congruent polygons

polygons with same size and shape

### circle

ellipse in which the two axes are of equal length

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

### diameter

The distance across a circle through its center. The line segment that includes the center and whose endpoints lie on the circle.

### central angle

An angle with a vertex at the center of a circle and whose sides are radii of the circle

### chord

line segment whose endpoints are any two points on a circle

part of a circle

Half of a circle