1. Points, Lines, & Planes

2. The 3 Undefined Terms in Geometry
Point
Represents location
Has no size
Line
Straight arrangement of many points
Has length but no width
Plane
Flat surface that continues forever
Has length and width but no thickness ●

3. Naming points • • • use a capital letter. To name a point,
points A, B, and C

4. Naming lines • • To name a line, use a lower case script letter OR
any two points on the line. • •
line m or
line AB or line BA

5. Naming planes • • • To name a plane,
use a capital script letter in the corner of the plane OR
use 3 non-collinear points on the plane. • • •
plane R, or
plane ABC, CBA, BAC, or any combination of the 3 points

6. Terms to Know • • • • • • Collinear points Coplanar points
points that lie on the same line
(A, B, & C are collinear points)
Coplanar points
points that lie on the same plane
(A, B, & C are coplanar points) • • • • • •

7. Terms to Know • Intersecting lines lines that share at least one point
lines j and k intersect at point X

8. Terms to Know Parallel lines
lines that lie in the same plane that do not intersect
lines j and k are parallel

9. Terms to Know Skew lines lines that are not in the same plane j k
that do not intersect and are not parallel j k
lines j and k are skew

10. Relationships between 2 different lines
Parallel
(no points in common)

11. Relationships between 2 different lines
Intersect
(one point in common)
lines k and j intersect at point X •

12. Relationships between 2 different lines
Skew
(no points in common)

13. Relationships between 2 different planes
Parallel
(no points in common)

14. Relationships between 2 different planes
Intersect
(intersect to form a line)

15. Relationships between a line and a plane
When a line lies on a plane,
the intersection is a line.

16. Relationships between a line and a plane
When a line is parallel to a plane,
there is no intersection.
When a line intersects a plane,
the intersection is a point.

17. Checking your understanding
What are the 3 undefined terms in geometry?
_______ points lie on the same plane.
_______ lines lie in different planes and do not intersect.
The intersection of 2 planes is a _______.
The intersection of 2 lines is a _______.
The intersection of a line and plane is a_______.
If 2 lines have no points in common, then they are _______.
What possible relationships exist when 3 planes intersect?

18. How well did you do? Point, line, and plane Coplanar points Skew lines
Parallel
They will intersect to form a line or a point.