# How to type math sign for neighbourhood in LaTeX?

Can you help me please, how to type the sign that is emphasized? It looks like mirror image of sign \partial

• Welcome to the TeX.SE....that symbol not correspond to partial but to the calligraphic O. – Sebastiano Aug 4 at 15:02

For example using mathrsfs package give to you the symbol O:
\documentclass[12pt]{article}
$\mathscr{O}$