# Thread: The $$\in$$ symbol

1. ## The $$\in$$ symbol

I'm reading my calc chapters and I don't know what this sign means. I thought I post it in the pre-algebra & algebra section because the symbol has nothing to do with calc.

So I was wondering what the symbol is called and what it means. Here it is: $\in$

It is used in context like this: The Cartesian product $\Re x \Re x \Re = { (x, y, z) | z, y, z \in \Re }$ is the set of all ordered triples of real numbers and is denoted by $\Re^3$

2. Originally Posted by lilaziz1
I'm reading my calc chapters and I don't know what this sign means. I thought I post it in the pre-algebra & algebra section because the symbol has nothing to do with calc.

So I was wondering what the symbol is called and what it means. Here it is: $\in$

It is used in context like this: The Cartesian product $\Re x \Re x \Re = { (x, y, z) | z, y, z \in \Re }$ is the set of all ordered triples of real numbers and is denoted by $\Re^3$
It means 'is an element of'.

3. Or, less formally, it means "in".

So $x \in \mathbf{R}$ means " $x$ is an element of the Real Numbers", or " $x$ is in the set of Real Numbers", or " $x$ is a Real Number"...