Is GRP a subcategory of SET, or not?
100245
Category of Grp is not a subcategory of Set
22498
In set theory, how are real numbers represented as sets?
104898
Proper notation for distinct sets
130418
Is ${\{\emptyset,\{\emptyset\},\{\{\emptyset\}\},\{\{\{\emptyset\}\}\},...\}} $ a set?
140752
Example of a recursive set $S$ and a total recursive function $f$ such that $f(S)$ is not recursive?
146891
Why is $\{\emptyset\} \not = \emptyset$?
74970
Subsubgroups are subgroups of subgroups / Multiplicative Property of the Index
58594
Is the empty set a subset of itself?
114968
Partition of a set, definition not clear
149926
ZFC with class terms: is any set also a class?
107215
Is $\emptyset \in \emptyset$ or $\emptyset \subseteq \emptyset$?
122110
Character of the subobject classifier in the topos of $\mathbf{M}$-sets.
155063
Is Cl(f(A)) a subset of f(Cl(A))?
47697
Russell's paradox: a set cannot contain its own powerset
30660
Empty set does not belong to empty set
62255
Notation question: Subroup generated by two elements?
141318
$\subset$ vs $\subseteq$ when *not* referring to strict inclusion