# Topology notation question

1. Oct 8, 2007

### ehrenfest

1. The problem statement, all variables and given/known data
I saw the following statement in a proof that a second countable normal space is homeomorphic to the Hilbert cube:

$$n = (B_i, B_j)$$

where the = sign is replaced with an approximately equals which I do not know how to make in latex

B_i and B_j are basis sets s.t. B_i closure is a subset of B_j

n is a natural number

Anybody know what the the approximately equal sign means (they already defined what the ordered pair was)?

2. Relevant equations

3. The attempt at a solution

Last edited: Oct 8, 2007
2. Oct 8, 2007

### matt grime

\sim is what you might want.

3. Oct 8, 2007

### morphism

Where did you see this? Can you give us a link, or book & page number?

By the way, you probably meant to say "homeomorphic to a subspace of the Hilbert cube".