# Correct reading of Set builder Notation?

could anyone please let me know the correct reading(sentence form) of set builder notation, confused with different interpretation in different resources.

Many Thanks

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## 1 Answer

The set $\{x\mid\varphi(x)\}$ is "The set of all $x$ such that $\varphi(x)$ holds." Note that sometimes such collection is not a set (e.g. the collection of all sets); and sometimes we wish to limit the elements to be taken from a certain set $A$.

The set $\{x\in A\mid\varphi(x)\}$ is "The set of all $x$ in $A$ such that $\varphi(x)$ is true."

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Many thanks for your reply. could you please clarify this "Note that sometimes such collection is not a set (e.g. the collection of all sets);" with some examples –  nish1013 Nov 9 '12 at 14:28
@nish1013: There are several paradoxes of naive set theory which show that certain collections cannot be sets. For example the collection of all sets (as I remarked in my answer). –  Asaf Karagila Nov 9 '12 at 14:29