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I'm using variables u, v, w in a lemma. However my latex compiler changes v to υ which then makes it difficult to distinguish between u and υ.

Why does it do this and how can I avoid it from happening?

I'm following the simple lemma format:

\begin{lemma}
\end{lemma}

\begin{proof}
\end{proof}

EDIT: After David's comment, I simplified my document to point out the problem:

\documentclass{article}
\usepackage[utf8]{inputenc}

\title{s}
\author{author}
\date{November 2014} 
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}

\begin{document}

\maketitle

\section{Introduction}

\begin{lemma}
Let $u$, $v$, $w$
\label{lemma4}
\end{lemma}

\end{document}
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    latex does not change v to upsilon unless you instruct it to do so, (and actually I can not think of a convenient way of instructing it to do that) please give a complete small document that shows the problem.
    – David Carlisle
    Nov 15, 2014 at 19:23
  • Hello David, thank you for your comment. I added the code that gives me this problem.
    – ksm001
    Nov 15, 2014 at 19:30
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    the math variables there are the same math italic as you would see in the rest of the document, the lemma is irrelevant isn't it? it is an italic v as is standard for mathematics, not an upsilon
    – David Carlisle
    Nov 15, 2014 at 19:34
  • Is it possible to use v as it is? Because it makes it very hard to tell the difference between υ and u then.
    – ksm001
    Nov 15, 2014 at 19:35
  • 1
    You could use \mathrm{v} but be going against all mathematics typesetting tradition
    – David Carlisle
    Nov 15, 2014 at 19:36

2 Answers 2

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12

the "curly" form of "v" has long been standard in mathematical typesetting to distinguish it from the greek "nu". the "w" is also changed for consistent style.

i've simplified your example a bit and added instances of nu and upsilon to show the difference.

output of example code

it is essential in math that each letter be recognizable by itself, with no additional context, to avoid misinterpretation. math fonts are specially designed precisely for this reason. (this is also the reason why many uppercase greek letters are not supported by tex -- because the shapes are identical to those in the latin alphabet.)

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    I've never found $v$ and \upsilon very easy to distinguish and generally avoid ever using \upsilon. And I think in a casual read, $w$ and \omega can be easily mistaken too (though, if you get used to a particular font, $w$ and \omega are distinguishable).
    – A.Ellett
    Nov 16, 2014 at 2:55
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    @A.Ellett -- good point. forgot about omega; added it. thanks. of course, a "real" reason that these letters are difficult to distinguish from one another is that they all ultimately come from the same writing tradition, based on the phoenician alphbet.
    – barbara beeton
    Nov 16, 2014 at 17:24
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If you're open to using a different math font try adding \usepackage[charter]{mathdesign} to your preamble.

enter image description here

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[charter]{mathdesign}

\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[theorem]
\newtheorem{lemma}[theorem]{Lemma}

\begin{document}
\section{Introduction}

\begin{lemma}
Let $u$, $v$, $w$
\label{lemma4}
\end{lemma}

\end{document}
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3
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    Of course, when using Times Roman italics, someone's going to complain that $v$ and $\nu$ look too similar...
    – Mico
    Nov 15, 2014 at 19:50
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    @Mico are you calling barbara someone :-)
    – David Carlisle
    Nov 15, 2014 at 23:21
  • @Mico -- after a noodge because my answer was just now accepted, i saw your comment. when times was used "in production" for math texts, the times "v" was traditionally substituted by that letter from a century font (i think schoolbook) to avoid the confusion with "nu", and "w" was also substituted to harmonize with the "v". i don't know for sure whether this was done just for math, or was also used in the text. but possibly both, since it would have been easier to handle on monotype.
    – barbara beeton
    Mar 11, 2015 at 20:09

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