Chapter 1 Geometry Vocabulary

Front 1

Point

Back 1

An undefined term thought of as a location with no size or dimension. It is the most basic building block of geometry. In a two dimensional coordinate system, a point´s location is represented by an ordered pair of numbers (x,y).

Front 2

Line

Back 2

An undefined term thought of as a straight and continuous arrangement of infinitely many points. It has infinite length but no thickness (one dimensional), and extends forever into two directions.

Front 3

Plane

Back 3

An undefined term thought of as a flat surface that extends infinitely along it's edges. A plane has length and width but no thickness, so it is two dimensional.

Front 4

Definition

Back 4

A statement that clarifies or explains the meaning of a word or phrase.

Front 5

Collinear

Back 5

On the same line.

Front 6

Coplanar

Back 6

On the same plane.

Front 7

Line Segment

Back 7

Two points and all the points between them that are collinear with the two points.

It is measured in length and also called a segment.

Front 8

Endpoints

Back 8

The points at either end of a segment or an arc or the first point of a ray.

Front 9

Congruent

Back 9

(Angles, lines, segments, or polygons) Identical in shape and size.

Front 10

Midpoint

Back 10

The point on the line segment that is the same distance from both endpoints. The midpoint bisects the segment.

Front 11

Bisect

Back 11

To divide into two congruent parts.

Front 12

Ray

Back 12

A point on a line, and all the points of the line that lie on one side of this point.

Front 13

Angle

Back 13

Two non-collinear rays having a common endpoint.

Front 14

Vertex

Back 14

A point of intersection of two or more rays or line segments in a geometric figure (vertices).

Front 15

Side (of an angle)

Back 15

One of the two rays that form an angle.

Front 16

Measure of an angle

Back 16

The smallest amount of rotation about the vertex from one ray to the other, measured in degrees

Front 17

Degrees

Back 17

A unit of measure for angles and arcs equivalent to 1/360 of the rotation around a circle.

Front 18

Reflex measure of an angle

Back 18

The largest amount of rotation less than 360 degrees about the vertex from one ray to another.

Front 19

Protractor

Back 19

A tool used to measure the size of an angle in degrees.

Front 20

Angle Bisector

Back 20

A ray that has its endpoint at the vertex of the angle and that divides the angle into two congruent angles.

Front 21

Incoming angle

Back 21

The angle formed between the path of an approaching object and the surface from which it rebounds. (Equal to Outgoing Angle)

Front 22

Outgoing Angle

Back 22

The angle formed between the path of a rebounding object and the surface it collided with. (Equal to Incoming Angle)

Front 23

Right Angles

Back 23

Angles that measure exactly 90º.

Front 24

Acute Angles

Back 24

Angles that measure less than 90º.

Front 25

Obtuse Angles

Back 25

Angles that measure more than 90º.

Front 26

Complementary Angles

Back 26

Angles that have measurements that together add up to 90º.

Front 27

Supplementary Angles

Back 27

Angles that have measurements that together add up to 180º.

Front 28

Vertical Angles

Back 28

Angles opposite to each other when two lines cross, that have congruent angle measurements.

Front 29

Linear Pair of Angles

Back 29

A couple of adjacent angles formed by intersecting lines that are also supplementary (add up to 180º).

Front 30

Polygon

Back 30

A closed figure in a plane, formed by connecting line segments endpoint to endpoint with each segment intersecting exactly with each other.

Front 31

Side (of the polygon)

Back 31

One of the line segments that form the polygon.

Front 32

Vertex (Of the polygon)

Back 32

A point of intersection of two or more rays or line segments in a geometric figure.

Front 33

Diagonal (of a polygon)

Back 33

A line segment that connects two nonconsecutive vertices.

Front 34

Convex (Convex Polygon)

Back 34

A polygon is Convex if no diagonal is outside the polygon.

Front 35

Concave (Concave Polygon)

Back 35

A polygon is concave if at least one diagonal is outside the polygon.

Front 36

Triangle

Back 36

A polygon with 3 sides.

Front 37

Quadrilateral

Back 37

A polygon with 4 sides.

Front 38

Pentagon

Back 38

A polygon with 5 sides.

Front 39

Hexagon

Back 39

A polygon with 6 sides.

Front 40

Heptagon

Back 40

A polygon with 7 sides.

Front 41

Octagon

Back 41

A polygon with 8 sides.

Front 42

Nonagon

Back 42

A polygon with 9 sides.

Front 43

Decagon

Back 43

A polygon with 10 sides.

Front 44

Undecagon

Back 44

A polygon with 11 sides.

Front 45

Dodecagon

Back 45

A polygon with 12 sides.

Front 46

Perimeter

Back 46

The length of the boundary of a two dimensional figure.

Front 47

Equilateral Polygon

Back 47

Polygon that has all congruent sides.

Front 48

Equiangular Polygon

Back 48

Polygon that has all congruent angles.

Front 49

Regular Polygon

Back 49

Polygon that has all congruent sides and angles.

Front 50

Assume

Back 50

To accept as true without facts or proof.

Front 51

Right Triangle

Back 51

A three sided polygon that has at least one right angle.

Front 52

Acute Triangle

Back 52

A three sided polygon that has all angle measures below 90º.

Front 53

Obtuse Triangle

Back 53

A three sided polygon that has at least one angle measures above 90º.

Front 54

Scalene Triangle

Back 54

A three sided polygon that has three different measures for each side.

Front 55

Equilateral Triangle

Back 55

A three sided polygon that has all congruent sides and angles.

Front 56

Isosceles Triangle

Back 56

A three sided polygon with two equal sides or two equal measures.

Front 57

Vertex Angle of an isosceles triangle

Back 57

The angles between two congruent sides.

Front 58

Base Angles

Back 58

The two angles opposite the two sides of equal length are called the base angles of the isosceles triangle.

Front 59

Trapezoids

Back 59

A quadrilateral with one pair of parallel sides.

Front 60

Kite

Back 60

A quadrilateral with two pairs of congruent sides that are not parallel.

Front 61

Parallelogram

Back 61

A quadrilateral with two pairs of parallel sides.

Front 62

Rectangle

Back 62

A plane figure with four straight sides and four right angles, especially one with unequal adjacent sides, in contrast to a square.

Front 63

Square

Back 63

A plane figure with four straight sides and four right angles.

Front 64

Space

Back 64

An undefined term thought of as the set of all points. Space extends infinitely in all directions, so it is three-dimensional.

Front 65

Isometric Drawing

Back 65

A drawing of a three-dimensional object that shows three faces in one view. Also called an edge view.

Front 66

Cylinder

Back 66

A solid consisting of two congruent, parallel circles and their interiors , and the segments having an endpoint on each circle that are parallel to the segment between the centers of the circles.

Front 67

Cone

Back 67

A solid consisting of a circle and its interior, a point not in the plane of the circle , and all points on line segments connecting that point to points on that circle.

Front 68

Prism

Back 68

A polyhedron with two congruent , parallel bases connected by lateral faces that are parallelograms.

Front 69

Pyramid

Back 69

A polyhedron consisting of a polygon base and triangular lateral faces that share a common vertex.

Front 70

Sphere

Back 70

The set of all points in space given at a given distance from a given point.

Front 71

Hemisphere

Back 71

Half of a sphere and its great circle base.

Front 72

Net

Back 72

A two dimensional pattern that can be folded to form a three dimensional figure.

Front 73

Circle

Back 73

A circle is the set of all points in a plane at a given distance from a given point.

Front 74

Radius

Back 74

A line segment from the center of a circle or sphere to a point on the circle or sphere. Also, the length of that line segment.

Front 75

Chord

Back 75

A line segment whose endpoints both lie on the circle, on the circle’s curve.

Front 76

Diameter

Back 76

A chord of a circle that contains the center, or the length of that chord.

Front 77

Tangent of a circle

Back 77

A line segment that just touches a curve of the circle at one point, without cutting across it.

Front 78

Point of Tangency

Back 78

The point of intersection of a tangent line and a circle.

Front 79

Concentric Circles

Back 79

Two or more coplanar circles sharing the same center.

Front 80

Arc

Back 80

Two points of a circle and the continuous part of the circle between them.

Front 81

Arc A

Semicircle

Back 81

An arc of a circle whose endpoints are the endpoints of a diameter.

Front 82

Arc B

Minor Arc

Back 82

An arc of a circle that is smaller than a semicircle.

Front 83

Arc C

Major Arc

Back 83

An arc of a circle that is larger than a semicircle.

Front 84

Central Angle

Back 84

An angle with its vertex at the center of the circle, and sides passing through the endpoints of the arc.

Front 85

Arc Measure

Back 85

The measure of the central angle that intercepts an arc, measured in degrees.