Math & Science ⇒ Italic fonts

[ubuntu2014]

I did some Google searches but couldn't find a pleasing answer.
Every time I write a formula in my LaTeX document, I see unnecessary italic fonts. Of course, the \mathrm command from amsmath package does well but many symbols like phi are still not straight. Is there any easy way to make it straight?

[Johannes_B]

Where are you from? In almost all parts of the world, variables are written in italics, operators are set upright, and many many other rules.
In mathematics, there is a difference between a, a and a.

[ubuntu2014]

But still I need to write them straight. Any suggestions?

[Stefan Kottwitz]

It depends on the used fonts. For example, you can switch to upright greek letters (and upright uppercase letters, which are also used for greek symbols) by

Code: Select all

\usepackage[upright]{kpfonts}

kpfonts is a nice set of fonts with a lot of features.

MinionPro with frenchmath option behaves similarly.

You can also get upright greek letters by

Code: Select all

\usepackage{upgreek}

and writing them as \upphi etc.

Stefan