Why $|\{\emptyset \}| =1$?
39333
The meaning of singleton and existence of $\{\varnothing, \{ \varnothing \}\}$
89712
For every set $A$, the empty set is a subset of $A$. The empty set is a set. Therefore, the empty set has a cardinality $\geq 1\ldots$
5230
Why can a 1 element set be a member of another set but not a subset of it?
13282
In the category $\mathbf{Set}$ is "the product of an empty set of sets a one-element set"?
113377
Empty preimage of an intersection implies empty intersection of the preimages
99480
Why is predicate "all" as in all(SET) true if the SET is empty?
79424
Don't understand proof that interior of a set is open
130418
Is ${\{\emptyset,\{\emptyset\},\{\{\emptyset\}\},\{\{\{\emptyset\}\}\},...\}} $ a set?
56233
Is the set of all strings with countably infinite length bijective to $[0,1]$?
2935
Completness and Set of Result of One Set ?!?
134050
Question about set notation: what does $]a,b[$ mean?
150825
Is an empty set equal to another empty set?
125317
Is this statement "Every element in the empty set is greater than itself." true or its negation is true?
36612
Strange set notation (a set as a power of 2)?
67066
Proof there is a 1-1 correspondence between an uncountable set and itself minus a countable part of it
132382
Showing a set is nowhere dense in $C([0,1])$
110677
How is an empty set truly "empty"?