Elementary set theory - are these sets empty?
32441
How to prove or disprove statements about sets
146891
Why is $\{\emptyset\} \not = \emptyset$?
111723
Can it be proven in $\sf ZF^{\neg\infty}$ that the sets $x_n=\{x_{n+1}\}$ do not exist?
66948
Proving question on sets
125077
what is the absolute value of a set?
109070
Question about the proof of the distributive property for sets
18828
Base and empty set of a topology
31212
The existence of the empty set is an axiom of ZFC or not?
3072
If the empty set is a subset of every set, why isn't $\{\emptyset,\{a\}\}=\{\{a\}\}$?
108922
Cardinality and infinite sets: naturals, integers, rationals, bijections
153551
Is the null set a subset of every set?
3663
Finding counterexamples in elementary set theory.
109219
How do the sets $\emptyset\times B,\ A\ \times \emptyset, \ \emptyset \times \emptyset $ look like?
58594
Is the empty set a subset of itself?
110957
No non-trivial clopen sets in $\mathbb{R}$? How to give a direct proof?
22391
Is the set of all pairs of real numbers uncountable?
28523
When would the intersection of the empty set mean anything?