How would you notate that something is not in the domain of discourse?

Question

For example, saying that something is specifically not in the domain of integers (not sure how to write the 'N' symbol).

Answer 1

Traditionally, the integers are denoted by $\mathbb{Z}$ which in Latex is written $\mathbb{Z}$. By enclosing Z in \mathbb{}, you are telling Latex to write Z in the math blackboard bold font, which is the standard font for sets of numbers. The natural numbers are denoted by $\mathbb{N}$, i.e. $\mathbb{N}$.

Mathematicians use an epsilon symbol to mean "is an element of." That is, $x \in \mathbb{Z}$ is read as "$x$ is an element of $\mathbb{Z}$." The Latex command for this epsilon is \in.

You want to say that something is not in the integers. To negate a statement, mathematicians often put a slash through a symbol. The statement $x \not\in \mathbb{Z}$ is read as "$x$ is not an element of $\mathbb{Z}$." The Latex command for this is $x \not\in \mathbb{Z}$. In general, prefixing a symbol with '\not' in Latex will put a slash through it.