$\textbf{Neighborhood}$
If $X$ is a topological space and $x\in X$, then a set $N\subset X$ is called a neighborhood of $x$ if there is an open set $U\subset N$ with $x\in U$.
$\textbf{Neighborhood}$
If $X$ is a topological space and $x\in X$, then a set $N\subset X$ is called a neighborhood of $x$ if there is an open set $U\subset N$ with $x\in U$.
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𝐍𝐞𝐢𝐠𝐡𝐛𝐨𝐫𝐡𝐨𝐨𝐝
If 𝑋 is a topological space and 𝑥∈𝑋, then a set 𝑁⊂𝑋 is called a neighborhood of 𝑥 if there is an open set 𝑈⊂𝑁 with 𝑥∈𝑈.