# What are the conventions regarding notation for variables denoting vectors?

Should a variable denoting a vector always be in upright font, even when it is a Greek letter?

When denoting vector variables, I have noticed that it is common to use a bold, non-italic, lowercase character, such as a, b, etc. I use latex for the few equations I write and I have noticed that it is quite cumbersome to create non-italicized lowercase Greek letters. This makes me wonder if Greek letter variables always should be italicized and it would be wrong to force an upright Greek letter for a vector variable.

What is the preferred way of typesetting a vector variable when it is represented by a Greek character? Should it be in italics and bold, or upright and bold?

### Update

Examples, from left to right: upright, bold+upright, italic, italic+bold. The upright letters are using a slightly different font in this example.

• I'm not sure I understand; do you think of for instance $\beta$ as being italicized? How would you make it non-italicized? Aug 17, 2016 at 15:52
• Not sure if there is a standard. For what it's worth, unless the context makes it clear what everything is, I like to include the arrow as in $\vec v$
– lulu
Aug 17, 2016 at 15:53
• @Lovsovs I added an image to better illustrate my question. Aug 17, 2016 at 16:04
• In economics (and I suppose many other fields) it is quite common not to use any special notation to distinguish vectors from scalars, e.g. just write $\beta=(\beta_1,\ldots, \beta_n)$. This seems neater to me, and leaves overlines etc free for other uses.
– smcc
Aug 17, 2016 at 16:35
• In France, Greek letters are traditionally upright. Aug 17, 2016 at 16:43

As you have noted, forcing Greek letters to be "non-italicized" is not very standard (if you want to use it anyway, see Bernard's comment below).

I'd do one of three things:

1. Bold: $\pmb{\beta}$
2. Overlined: $\overline{\beta}$
3. With an arrow: $\vec{\beta}$

To me, the bold option (no. 1) reminds me more of matrix notation, so I'd personally use either 2. or 3.

• It exists in quite a few font package, and is often known as frenchmath. To mention a few ones: fourier, kpfonts, Minion Pro, mathdesign, newpx or newtx. Aug 17, 2016 at 16:41
• @Bernard Thanks, great to know! Aug 17, 2016 at 16:48
• Thanks, in the end I went with the same notation as for any other variable, an italic beta with normal font weight and no added arrows or lines, $\beta$. The other solutions sometimes looked a bit cramped or unclear, such as when transposing the matrix, $\vec{\beta}^T$. It is possible that I can get around that playing with the space between characters, but I don't want to spend too much time optimizing that. Aug 23, 2016 at 1:14
• @cheflo Probably a good decision. Note that you could also use $\underline{\beta}$ for vectors and $\underline{\underline{\beta}}$ for matrices. $\underline{\underline{\beta}}^T$ looks pretty nice IMO. Aug 23, 2016 at 13:54