Can we say that the class of sets forms a monoid under set union?
133727
Is it possible to have a monoid with a proper class as the collection of elements?
81406
Does every set have a group structure?
30329
Why is the collection of all groups a proper class rather than a set?
46875
The identity morphism in $\mathbf{Set}$ is the identity function
21610
The monoid of fractions associated with the submonoid of cancellable elements of a commutative monoid E
27899
Can we prove the existence of $A\cup B$ without the union axiom?
110018
Conjugacy classes in $A_n$.
26530
What does the big intersection or union sign of a set mean?
156459
infinite monoid H that is not a free monoid and contains a free monoid as a submonoid
28539
Does any uncountable set contain two disjoint uncountable sets?
64871
Closure of Union contains Union of Closures
122271
A subset of a transitive set is transitive
104274
Express $C$ interms of the sets $A_n$
67279
Is the union of finitely many open sets in an omega-cover contained within some member of the cover?
138273
Terminology for a monoid with a total ordering on the elements?
140668
Union of $2$ set $A, B$ where $ A$ is a subset of $B$
30231
The boundary of union is the union of boundaries when the sets have disjoint closures