Why is $\{\emptyset\}\not\subseteq\{\{\emptyset\}\}$ true?
858
Is $\{\emptyset\}$ a subset of $\{\{\emptyset\}\}$?
43024
Well-ordered sets, properties of an element that is not largest in the set
10472
Is every set a subset?
44160
Set theory: difference between belong/contained and includes/subset?
56637
In naive set theory ∅ = {∅} = {{∅}}?
109070
Question about the proof of the distributive property for sets
143003
$\bigcup \emptyset$ is defined but $\bigcap \emptyset$ is not. Why?
146098
Number of nonempty subsets of a set with $n$ elements
130771
Sets and the principle of inclusion and exclusion
84609
Unary intersection of the empty set
36721
Is "The empty set is a subset of any set" a convention?
153551
Is the null set a subset of every set?
150825
Is an empty set equal to another empty set?
272
Cantor Sets/nonempty/cardinality
4213
The set that only contains itself
125317
Is this statement "Every element in the empty set is greater than itself." true or its negation is true?
34099
Proving that the empty set is unique