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I'm trying to learn category theory and I have a doubt with the Set category. According to Wikipedia https://en.wikipedia.org/wiki/Category_of_sets empty sets are the initial objects, which have morphisms to categories each one containing a set.

It says that singletons are terminal objects but as far as I understand, it's possible to have a morphism from a singleton to another singleton. Say A={e1} and B={e2} are singletons, one could have the morphism = <{e1}, {(e1, e2)}, {e2}> which should generate an arrow from {e1} to {e2}, making {e1} non-terminal.

What am I assuming wrong? it it possible that f is instead of a subset of AxB, is a strict subset?

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    Terminal doesn't mean there are no morphisms from it. It means that there is only one morphism to it from any given object. "$T$ is [terminal](https://en.wikipedia.org/wiki/Initial_and_terminal_objects) if for every object $X$ in $\mathbf C$ there exists a single morphism $X → T$." – 2017-01-07
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    Yes, I misunderstood what a terminal object is. – 2017-01-07

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