Points
• Undefined term
• No length, width, or thickness
• Named with a capital letter
Lines
• Undefined term -- No thickness
• Length that goes on forever in two
directions
Naming Lines
Intersecting Lines
Lines that share a point.
Y
n
m
Lines m and n intersect.
Point Y is the point of intersection.
Parallel Lines
Lines in the same plane that do not
intersect; planes that do not intersect.
k
j
Lines k and j are parallel.
k || j
Skew Lines
Lines that do not lie on the same
plane. (They do not intersect and
are not parallel.)
Plane
• Undefined Term
W
• No thickness
•Extends indefinitely
in all directions
Plane ABC
Plane W
Parallel Planes
Planes not intersect.
R
S
Planes R and S are
parallel.
Collinear
Points that are on the same line.
A
B
C
Points A,B and C are collinear.
Non-collinear
Points that are not on the same line.
A
B
Points A,B and C are non collinear.
C
Coplanar Points
Points that lie on the same
plane.
S
Q
P
R
Points P,Q, and R are coplanar.
Non-Coplanar Points
Points that do not lie on the
same plane.
S
Q
P
R
Points P,Q,R and S are non-coplanar.
Coplanar Lines
Lines that lie on the same plane.
x
y
Lines x, y are coplanar.
Postulates
Statements that are accepted as
true.
Theorems
Statements that are proven to be
true.
Postulate
If two lines intersect, their
intersection is a point.
n
P
m
Lines m and n intersect
at P.
Postulate
For any two points, there is
exactly one line through the
points.
B
A
l
Line l is the only line through
A and B
Postulate
For any three noncollinear points,
there is exactly one plane through
the points.
B
Q
C
A
Points A, B, and C lie in Plane Q.
Postulate
If two lines intersect, then they
are coplanar.
n
m
Lines m and n lie in only one plane.
Postulate
If two planes intersect, their
intersection is a line.
Z
W
k
Planes W and Z intersect in line k.
Postulate
Every plane contains at least
three noncollinear points.
Y
X
A
Z
Plane A contains points X, Y and Z.
Postulate
Every line contains at least
two points.
B
A
p
Line p contains points A and B.
Postulate
There is exactly one plane
containing a given line and a point
not on the line.

C

D
T
Only one plane contains T and CD.
Postulate
If a line and a plane intersect,
their intersection is a point or a
line.
t
Y
w
X
I
Line t intersects Plane x at I.
Line w intersects Plane Y at line w.
Source
http://www.hbschool.com/glossary/
math/glossary8.html