# Geometry 3rd Quarter

## 46 terms

### ray

A never ending straight path that goes in one direction

### plane

a set of all points on a flat surface extending in all directions

### segment

Part of a line between to endpoints

### line

a never ending straight path that goes in both directions

### perpendicular lines

Two lines that intersect to form right angles

### intersecting lines

lines that cross at one point

### parallel lines

lines in the same plane that never intersect

### intersecting planes

planes that meet at a line

### parallel planes

planes that do not intersect

### perpendicular planes

planes that intersect at a right angle

### right angle

an angle that measures exactly 90 degrees

### straight angle

an angle measuring 180 degrees

### acute angle

An angle less than 90 degrees

### obtuse angle

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

### vertex

The common endpoint of an angle

### congruent

Having the same size

### polygon

a closed plane figure formed by three or more line segments

### trapezoid

exactly 1 pair of parallel sides

### parallelogram

opposite sides are congruent and parallel

### rectangle

a parallelogram with 4 right angles

### rhombus

a parallelogram with 4 congruent sides

### square

a parallelogram with 4 right angles and 4 congruent sides

### supplementary angles

Two angles whose sum is 180 degrees

### complimentary angles

Two angles that add up to 90 degrees

### isosceles triangle

a triangle with two congruent sides

### obtuse triangle

a triangle with 1 obtuse angle

### equilateral triangle

A triangle with 3 congruent sides and 3 congruent angles

### scalene triangle

a triangle with no congruent sides

### right triangle

a triangle with one 90 degree angle

### acute triangle

A triangle with three angles less than 90 degrees.

### 180 degrees

The sum of the angles of a triangle

### 360 degrees

Number of degrees in a circle and in quadrilaterals

a polygon with four sides

### pentagon

a five-sided polygon

### hexagon

a polygon with 6 sides

### octagon

A polygon with 8 sides

### diameter

the distance across a circle through its center

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

### point

a single location or position

### regular polygon

a polygon with all sides and all angles equal

### translation

A transformation that "slides" each point of a figure the same distance in the same direction.

### reflection

A transformation that "flips" a figure or mirror image.

### rotation

Turning around an axis or center point.

### dilation

A transformation that changes the size of an object, but not the shape.

### scale factor

the ratio used to enlarge or reduce similar figures

### similar figures

figures that have the same shape but not necessarily the same size