# In notation

In math­e­mat­ics, the no­ta­tion $$x \in X$$ (where $$\in$$ is writ­ten “\in” in LaTeX) means that $$X$$ is a set and $$x$$ is an el­e­ment of that set.

# Examples

$$r \in \mathbb{R}$$ means that $$r$$ is a real num­ber.

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