Set Theory Vocabulary
Foldable
1. Hold paper landscape.
The side with the lines should be facing you.
2. Fold edges to the center.
Now the side with the lines will be on the
inside.
Element

Intersection
Subset
of a Set

Complement
of a Set

Union
Element
Definition & Example
A collection of items
or members of a set
Set A = {1,3, 5, 7, 9}

7 
1
2

A
A
A
Subset of a Set
Definition & Example
A collection of items
drawn entirely from
a single set.
-Can range from no
elements (null
subset) to all items
from a single set.
A = {Sports equipment}
B = {basketball, football,
tennis racket}
C= {fingernail polish, coffee}
B
C


A
A
{ } or
 A
Complement of a Set
Definition & Example
The set of all
elements NOT in a
set
U (universal set) =
{0,1,2,3,4,5,6,7}
A = {0,1,2,3}
A’ = {4,5,6,7}
Intersection
Example & Definition
U = {1,…,12}
X = {1,2,3,4,5,6}
Y = {3,4,7,8,11}
Z = {4,5,6,9,10,11}
X
Y
Z = {4}
The set of all
elements that are in
common between 2
or more sets
Union
Example & Definition
U = {alphabet}
A = {a,b,c,d,e}
B = {vowels}
A
B = {a,b,c,d,e,i,o,u}
The set containing
ALL of the elements
of 2 or more sets.