# What is this symbol, and how to reproduce it? (vertical bar with small footer) [duplicate]

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How to reproduce this symbol, using Latex, that consists of a long vertical bar, on the right hand side of an expression, and some small text at the bottom, that defines some condition? How to reproduce this symbol using latex?

## marked as duplicate by ChrisS, CarLaTeX, user2478, TeXnician, Stefan PinnowSep 30 '17 at 6:28

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• It is given in LaTeX as \vert and it is extensible, as in \left. \frac{...}{...}\right\vert_{...} – Steven B. Segletes Sep 29 '17 at 16:43
• @egreg fair enough. updated. how does the question look now? – Hugh Perkins Sep 29 '17 at 18:45

## 2 Answers

The basic building bloc is \vert. Because it is extensible, you have various ways to make it grow.

The various forms of $B/b]ig[g] grow it a defined amount, whereas the use as part of a \left...\right context grows it to fit the content. \documentclass{article} \begin{document} \[ A\vert_x$
$\frac{A}{B}\bigr\vert_x \frac{A}{B}\Bigr\vert_x \frac{A}{B}\biggr\vert_x \frac{A}{B}\Biggr\vert_x$
$\left.\frac{\displaystyle\frac{A}{B}}{\displaystyle1 + \frac{C}{D}}\right\vert_x$
\end{document} • Interesting—I've always used \Big|_{x}. Should I prevert to substitute \vert for |? – wchargin Sep 29 '17 at 21:29
• @wchargin In general | and \vert are completely equivalent. Indeed, \vert is defined as \delimiter "026A30C and the \delcode of | is 26A30C, while its \mathcode is 026A. – egreg Sep 29 '17 at 22:37

Just for training

\documentclass{article}
\usepackage{amsmath,amssymb}

\begin{document}
$+\Delta\mu_{i}\left.\frac{\partial E_{S\sim\mathcal{N}(\mu,\sigma^{2}_{S})}[f(S)]}{\partial \mu}\right\vert_{\mu=\mu_{S}}$
\end{document} 