Geometry Vocabulary Packet

Mrs. Jenkins8th Grade Mathematics

1.POINT:a mathematical figure pictured by a dot and named by a letter.

• CAPITAL LETTERB

2. LINE: a line segment extended without end in both directions.

B D C

BD�������������� �

BC�������������� �

DC�������������� �

3. LINE SEGMENT: a part of a line consisting of two endpoints and all the points between them.

B D C

BD BC DC

4. RAY:a line segment extended without end in one

direction only.B D C

BD��������������

BC��������������

DC��������������

CB��������������

NOT

5.COLLINEAR POINTS: points that lie on the same line.

B D C

B, D and C are collinear with each other

E is not collinear with B, D and C

E

6.ENDPOINT: a boundary point of a line segment or ray.

B D C

BD��������������

The endpoin

t is B

BC The endpoints are B and

C

7. PLANE: a set of points on a flat surface that extends without end.

8.COPLANAR: points or lines in the same plane.

9.COMPASS: a drawing instrument used to draw arcs and circles.

10.CIRCLE: a plane figure with all points the same distance from a given point called the center. T

Named for its center

point:

Circle T

U

S

VT

R

Copy this diagram onto your packet.

It will used as a reference for the next six terms.

11.CHORD: a segment with both endpoints on the circle.

U

S

VT

R RU

SU

12.DIAMETER: in a circle, a segment that passes through the center and that has both endpoints on the circle.

U

S

VT

R

RU

13.ARC: part of a circle.

U

S

VT

R

RS

SU RSU

RUS

Are

the same arc?

14.SEMI-CIRCLE: an arc that joins the endpoints of a diameter.

U

S

VT

R RSU

15.RADIUS: in a circle, a segment that has one endpoint on the circle and the other endpoint on the center of the circle.

U

S

VT

RRT

TU

16.TANGENT: a line that intersects a circle in exactly one point.

U

S

VT

R

SV�������������� �

17.CIRCUMFERENCE: the distance around a circle.

2C rC d

T

18.PI: the ratio of a circle’s circumference divided by its diameter.

C

D

Review #1-18

Name the six rays.

W X Y

19.ANGLE: the figure formed by two rays sharing a common endpoint called a vertex.

20. SIDE:a.one of the rays of an

angleb. a line segment whose

endpoints are adjacent vertices of a polygon. side

side

21. VERTEX: (Vertices)

a. the common endpoint of two rays that form an angle.

b. the point of intersection of two sides of a polygon.

c. the point of intersection of the edges of a polyhedron.

vertex

vertex

vertex

22.ADJACENT ANGLES: angles that have a common vertex and share a common side between them.

1

23

4

5

1& 5 5& 2 3& 2 3& 4 4 & 1

23.VERTICAL ANGLES: angles formed by intersecting lines and sharing only a vertex.

2 & 4 1

23

4

5

Look for the Bow Tie!

24. PROTRACTOR: a device for measuring angles in units called degrees.

25. BISECT: to divide into two

congruent parts.

26.ACUTE ANGLES: an angle whose measure is between 0 and 90.

27. RIGHT ANGLES: an angle whose measure is 90

28. OBTUSE ANGLES: an angle whose

measure is between 90 and 180.

29. STRAIGHT ANGLES: an angle whose measure is 180.

30. PERPENDICULAR LINES: lines that intersect to form right angles.

31. EQUAL ANGLES: angles with the same measure.

32. COMPLEMENTARY ANGLES: angles whose measures add up to 90.

33. SUPPLEMENTARY ANGLES: angles whose measures add up to 180.

Keeping them Straight!

Some ways to remember…

Alphabetical and Numeric OrderComplimentary 90Supplementary 180

Supplementary

Straight Line 90 180c S

34. CENTRAL ANGLE: an angle with its vertex at the center of the circle.

35.POLYGON: a closed plane figure made by line segments.

NOT Polygons…

WHY?

36.REGULAR POLYGON: a polygon with all sides congruent and all angles congruent.

37.TRIANGLE: a polygon with 3 sides.

The sum of the measure

of the interior angles of a triangle

must be 180

Can these side lengths make a triangle?

5, 7, 39, 5, 2

How do you know?The sum of the 2 smaller side lengths

must be greater than the length of the longest side.

Triangle Classification

By Angle Measure

38.Acute Triangle

39.Obtuse Triangle

40.Right Triangle

By Side Lengths

41.ScaleneTriangle

42.IsocelesTriangle

43.Equilateral Triangle

38. ACUTE TRIANGLE: a triangle with three acute angles.

39. OBTUSE TRIANGLEa triangle with an obtuse angle.

40.RIGHT TRIANGLE: a triangle with a right angle.

41.SCALENE TRIANGLE: a triangle with no congruent sides.

42.ISOSCELES TRIANGLE: a triangle with at least two congruent sides.

43.EQUILATERAL TRIANGLE: a triangle with all three sides congruent.

9

54

37

6

28

1

Adjacent Angles (9 pair)

Vertical Angles (3 pair)

Supplementary Angles (10 pair)

Complimentary Angles (1 pair)

Quadrilateral Diagram

44.QUADRILATERAL: a polygon with 4 sides.

45.TRAPEZOID: a quadrilateral with exactly one pair of parallel sides.

46.ISOSCELES TRAPEZIOD: a trapezoid with non parallel sides congruent.

47.PARALLELOGRAM: a quadrilateral with opposite sides parallel and congruent.

48.RHOMBUS: a parallelogram with all sides congruent.

49.RECTANGLE: a parallelogram with four right angles.

50.SQUARE: a rectangle with congruent sides or a rhombus with four right angles.

51.PENTAGON: a polygon with 5 sides.

Why is the Pentagon called the Pentagon?

5 Branches ofMilitary• Army• Navy

• Marine Corps• Air Force

• Coast Guard

52.HEXAGON: a polygon with 6 sides.

53.HEPTAGON: a polygon with 7 sides.

54.OCTAGON: a polygon with 8 sides.

55.NONAGON: a polygon with 9 sides.

Construct your own or use Sketcher # 24

56.DECAGON: a polygon with 10 sides.

Construct your own or use Sketcher # 25

57.CONGRUENT POLYGONS:polygons that are the same shape and size.

58. SIMILAR POLYGONS: polygons that are the same shape and proportional in size.

59.DIAGONAL: a segment with two non-adjacent vertices of a polygon as its endpoints.

How many diagonals can be drawn…

• From one vertex of a pentagon?

• From all vertices of a pentagon?

60.SYMMETRIC FIGURE: a plane figure that can be folded into two congruent parts. The fold is the line of symmetry.

For the #61-74, we will be using the below diagram

Q X 1 2 Y

3 4

W 5 6 Z 7 8 P

61.PARALLEL LINES: coplanar lines which never intersect.

Q X 1 2 Y

3 4

W 5 6 Z 7 8 P

XY WZ���������������������������������������� ���

62.TRANSVERSAL: a line which intersects two or more lines in the same plane (cuts the

parallel lines) Q X 1 2 Y

3 4

W 5 6 Z 7 8 P

QP�������������� �

63.ALTERNATE INTERIOR ANGLES:

angles between parallel lines and on opposite sides of the transversal

(look for the Z) Q X 1 2 Y

3 4

W 5 6 Z 7 8 P

3& 6

4 & 5

64.CORRESPONDING ANGLES: angles having the same position on each of the parallel lines (look for the F)

Q X 1 2 Y

3 4

W 5 6 Z 7 8 P

1& 5 2 & 6 3& 7 4 & 8

65.SKEW LINES: lines which are not coplanar, do not intersect and are not parallel.

Extra Credit Opportunity

Find 10 pictures (not clip art!) that display real life examples of 10

Geometry Vocab Words

Example: Skew Lines