# How to distinguish r and gamma, w and omega, v and nu?

Haorong Wu
How to distinguish ##r## and ##\gamma##, ##w## and ##\omega##, ##v## and ##\nu## and ##\upsilon##?

They look very similar. Are there some rules that I should use one of them in some specific cases?

weirdoguy

Mentor
How to distinguish ##r## and ##\gamma##, ##w## and ##\omega##, ##v## and ##\nu## and ##\upsilon##?

They look very similar. Are there some rules that I should use one of them in some specific cases?

No they don't. Not when written like you did in Latex...

Homework Helper
Gold Member
There's also
$\rho$ and $p$, $\chi$ and $x$, $\kappa$ and $k$, $\tau$ and $T$,
$\gamma$ and $Y$ , $\eta$ and $n$, $\beta$ and $B$, $\epsilon$ and $E$,
and, finally, (iota) $\iota$ and $i$ and (omicron) $\omicron$ and $o$ and (upsilon) $\upsilon$ and $u$ or $v$.

If handwritten, the chance for confusion is higher.

What's sometimes annoying is having people call $\rho$ "$p$", etc..

It's probably best to stick to common conventions.
I like to spell out the letter if I feel that confusion can arise.
e.g., the pressure $p$ and the density (rho) $\rho$ are related by $p = p_0 +\rho g h$

Mentor
It's the Westerners' revenge for having to learn hundreds of characters when studying Chinese.

Mono field, Haorong Wu, Wrichik Basu and 3 others
Mentor
More seriously, I think there are two different things that you need to watch for, coming from a language such as Chinese:

1. In textbooks and in LaTeX, mathematical formulas use the Latin alphabet in a different font (typeface) than in ordinary print:

Math: ##a\, b\, c\, d\, e\, f\, g\, h\, i\, j\, k\, l\, m\, n\, o\, p\, q\, r\, s\, t\, u\, v\, w\, x\, y\, z##
Ordinary print: a b c d e f g h i j k l m n o p q r s t u v w x y z

2. Mathematical formulas often use the Greek alphabet which is different from the Latin alphabet.

Greek math: ##\alpha\, \beta\, \gamma\, \delta\, \cdots##

You simply have to become familiar with the Greek alphabet and pay attention to characters which look similar to (but not identical with) Latin characters, e.g. ##\omega## "omega" versus ##w## "double-u" (in English; other languages have different names for it), or ##\rho## "rho" versus ##p## (p). My (American) students in introductory physics classes also often had trouble with these. Also with ##\kappa## "kappa" versus ##k## (k), and ##\alpha## "alpha" versus ##a## (a). It simply needs practice and memorization.

Mono field
How to distinguish ##r## and ##\gamma##, ##w## and ##\omega##, ##v## and ##\nu## and ##\upsilon##?

It is not possible except by knowing the convention and context. I had a lecturer who did not know or did not want to pronounce ##\xi## the conventional way, and called it "squiggle". It was fine as everyone understood the physics he intended to communicate.

etotheipi and wukunlin
2022 Award
I had the misfortune to be the first English person two Greek students saw after they worked out that when us English people said "fie" we meant ##\phi##. It's apparently pronounced more like "fee", although with a shorter e sound. I have a feeling I could have learned quite a lot of bad language in Greek that day... It had been quite a problem for them because there was (to them) a mismatch between what was being said and what was being written.

I must say that if I'm using ##v## for velocity I'll typically use ##f## for frequency instead of ##\nu## to avoid confusion. And I hate working with the dust stress-energy tensor because it's ##\mathrm{diag}(\rho,p,p,p)## and I have to be very careful not to mix up density and pressure.

I suppose that all I'm really offering is sympathy. You do get used to knowing that people use rho for density, and then you're primed to look for the difference (the top left of a ##p## is different to a ##\rho##).

Mentor
Do physicists or mathematicians actually use ##\upsilon## (lower-case Greek upsilon) for anything? I can't remember any examples. Of course, I'm familiar with ##\Upsilon## (upper-case upsilon) as the name of a particle.

Staff Emeritus
I've seen it used as a variable index in really gnarly equations.

Haorong Wu
There's also
$\rho$ and $p$, $\chi$ and $x$, $\kappa$ and $k$, $\tau$ and $T$,
$\gamma$ and $Y$ , $\eta$ and $n$, $\beta$ and $B$, $\epsilon$ and $E$,
and, finally, (iota) $\iota$ and $i$ and (omicron) $\omicron$ and $o$ and (upsilon) $\upsilon$ and $u$ or $v$.

If handwritten, the chance for confusion is higher.

What's sometimes annoying is having people call $\rho$ "$p$", etc..

It's probably best to stick to common conventions.
I like to spell out the letter if I feel that confusion can arise.
e.g., the pressure $p$ and the density (rho) $\rho$ are related by $p = p_0 +\rho g h$

I wonder whether there is a table listing convention usages.

After all, when I continue reading more and more textbooks, there are more and more symbols and quantities that I am not so familiar with as ##\rho## for density, ##p## for pressure, etc. It is difficult for me to clearly figure out which symbol I am encountered.