2. The Undefined Terms
There are three terms that have no definitions, but
we can describe them. They are the building blocks
that we use to define other terms.
1. Point – a location in space
How many dimensions does
A• a point have?
Point A Zero!
Note: A capital letter is used. (It really has no size.)
3. The Undefined Terms
2. Line – extends in two directions without ending
⋅
l How many dimensions
A B does a line have?
AB, or line l One!
(length)
Note: It can be named using a
lower-case letter or by referring to
two points on the line.
(It has no width.)
4. The Undefined Terms
3. Plane – extends in all directions without ending,
has no thickness
How many dimensions
does a plane have?
M
N Two!
Horizontal
Vertical
(length and
Plane M width)
Plane N
Note: Name using capital letters.
5. Some More Vocabulary
Space – the set of all points
Three dimensions – length, width, and height
Collinear Points – points all on the same line
Collinear Points
Noncollinear Points
7. Some More Vocabulary
Intersection – the set of all points common to
all figures
2 lines intersect A line & a plane
in a point intersect in a point 2 planes intersect
or a line in a line
8. Now, Some Practice!
Classify each statement as true or false
1. P is in M
N
2. b is in M
X 3. YX contains P
b
A 4. M contains YX
M
5. A is on b
Y
P 6. A and P are in M
7. N contains P
9. More True or False!!!
8. PF ends at P.
9. Point S is on an infinite number of lines.
10. A plane has no thickness.
11. Collinear points are coplanar.
12. Planes have edges.
13. Two planes intersect in a line segment.
14. Two intersecting lines meet in exactly one point.
15. Points have no size.
16. Line XY can be denoted as XY or YX.
