I have started seeing the "∈" symbol in math. What exactly does it mean?

I have tried googling it but google takes the symbol out of the search.

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    $\begingroup$ It means "belongs to". For instance $x\in A$ means that the element $x$ belongs to $A$. $\endgroup$ Jun 25, 2014 at 5:27
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    $\begingroup$ By pure coincidence I was just searching how to input this symbol in mathjax! $\endgroup$
    – Chinny84
    Jun 25, 2014 at 5:34
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    $\begingroup$ You could try googling "mathematical symbols"... $\endgroup$
    – user147263
    Jun 25, 2014 at 5:46
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    $\begingroup$ Google doesn't support this at the moment, but Wikipedia does. Enter it in the search or put it in the URL. Take these examples: , and . $\endgroup$ Jun 25, 2014 at 9:47
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    $\begingroup$ $8$ up votes for this :O $\endgroup$
    – user87543
    Jun 25, 2014 at 11:41

3 Answers 3


$\in$ means '(is) an element of'

For instance, 'Let $a\in A$' means 'Let $a$ be an element of $A$'

http://en.wikipedia.org/wiki/Element_(mathematics) might help you too

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    $\begingroup$ Being only a freshman going into Honors Algebra Two, I don't understand the concept. But thanks for the answer, even if I don't understand the concept at least I know what it means. $\endgroup$
    – Locke
    Jun 25, 2014 at 5:31
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    $\begingroup$ @Locke Look at the link I added too $\endgroup$ Jun 25, 2014 at 5:32
  • $\begingroup$ Thanks for the link. The information on that Wiki really cleared it up for me. $\endgroup$
    – Locke
    Jun 25, 2014 at 5:35
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    $\begingroup$ An added note, since the wiki article does not mention it: one can look at ∈ meaning 'is' through the prism of sets representing the common property held by all its elements. e.g. Even = {0,2,4,..} and 'a ∈ Even' can be read as 'a is Even' $\endgroup$ Jun 25, 2014 at 11:37

(mathematics) means that it is an element in the set of… For eg...x ∈ ℕ denotes that x is within the set of natural numbers.

The relation "is an element of", also called set membership, is denoted by the symbol "∈". Writing {\displaystyle x\in A} x\in A means that "x is an element of A". Equivalent expressions are "x is a member of A", "x belongs to A", "x is in A" and "x lies in A". The expressions "A includes x" and "A contains x" are also used to mean set membership, however some authors use them to mean instead "x is a subset of A".

Another possible notation for the same relation is {\displaystyle A\ni x,} A\ni x, meaning "A contains x", though it is used less often. The negation of set membership is denoted by the symbol "∉". Writing {\displaystyle x\notin A} x\notin A means that "x is not an element of A".

  • $\begingroup$ "contains" and "lies in" are also a very bad words to use here, as it refers to inclusion, not set membership-- two very different ideas. $\endgroup$ Nov 10, 2019 at 3:21

$\in$ means "Element of".

For example, $a \in A$ means Element of: $a$ is in $A$.

A numeric example would be: $\color{red}3 \in \{1, 2, \color{red}3, 4, 5\}$.


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