In topology, what is a basis for a topology on a set $X$?
Question 2
Which family of sets is a basis for the standard topology on $\mathbb{R}$?
Question 3
What is a subbasis for a topology on a set $X$?
Question 4
Suppose a collection $\mathcal{B}$ of subsets of $X$ is a basis. Which statement must be true for every point $x \in X$ and every open set $U$ containing $x$?
Question 5
Which description best explains how a topology is generated from a subbasis?
