Definition talk:Doubleton

Definition Question
To formalize this, a doubleton is simply the union of two singletons - that is $\{ A,B \} = \{ A \} \cup \{ B \}$. However, the descriptive definition given here is not enough to deduce this, because we cannot tell whether A and B need to be distinct sets. -Andrew Salmon 00:39, 15 September 2011 (CDT)


 * You're only looking at this from the point of view of pure set theory, where the only elements allowed are sets themselves. This page should cover both outlooks. --prime mover 00:42, 15 September 2011 (CDT)


 * True, it's easier to understand this more intuitively via the definition given. Andrew Salmon 00:45, 15 September 2011 (CDT)

Distinctness
For the set theory definition, don't you have to add $a \ne b$? --GFauxPas (talk) 02:04, 25 October 2012 (UTC)


 * Words have been added to specify that $a$ and $b$ are distinct. --prime mover (talk) 17:17, 23 January 2020 (EST)