Ugly spacing around f in math mode
Solution 1
For a detailed answer why this is happening you can read this answer of mine (shameless plug indeed): In short, the italic correction of the f
has a great part in this. But the italic correction only explains the spacing after the f
, not before. For this you have to look at the bounding boxes of the letters:
The first f
is a text italic letter in its bounding box, the second one is math italic (in its bounding box together with its italic correction). As you can see, the text letter protrudes a bit to the left (and a lot to the right); the math letter has a tiny bit of white space in the left (and also in the right, because of the italic correction). For a bit more about the bounding boxes see this question of mine (another shameless plug :)
).
I first noticed the problem when typing $Vf$
, which doesn't yield a nice output. My resort is using $V\hspace{0.1em}f$
instead (in a macro, of course), which I like much better. You could even use $V\!f$
, but this I find too narrow. Compare these three:
I would not encourage you to follow Caramdir's (now removed) suggestion to use $\mathit{Vf}$
since this uses a different font (text italic, not math italic). You can see quite clearly that the V
is narrower (in other words, the angle at the bottom of the V
is more acute):
If you use a different math font (like Euler), then the difference is even more noticeable.
(For a case where \textit
could be a good solution, see this answer of TH.)
Solution 2
Math mode considers each symbol a separate variable, not part of a "word". If you want wordlike behaviour, use \mathrm{...}
or \mathit{...}
. If this really is a product, perhaps using \cdot
between factors (or reorganizing, or changing variable names, perhaps distinguished by subindices) helps.
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Comments

A. Rex over 1 year
My paper contains many math expressions like
$abcde$
or$abdefv$
. Unfortunately, the latter looks very ugly, particularly in regards to the spacing around thef
. In particular, there is a significant amount of space around thef
which is not present around the other letters.Is there a method to make that spacing tighter?
Note: Joseph Wright suggested using
\!
to get a negative thin space. This does seem to help. But I'm still a bit curious as to why the problem occurs at all. For example, it looks fine in$acdfv$
before thef
but not after. If anyone has some more details on why the spacing ends up as it does, please comment. Thanks.
Joseph Wright almost 13 yearsSeems like a very unlikely product  do you really mean this? If so, perhaps try
\!
to back the spacing up. 
A. Rex almost 13 years@Joseph Wright: Yes, that's an actual example from my paper, but $efv$ has the same problem and isn't as unlikely. Thanks for the $\!$ advice  I guess I should have thought about that. That works before the $f$ quite well. Is there a predefined way to get an even thinner negative space (for after the $f$) or should I use $\hspace{..}$?

Matthew Leingang almost 13 yearsSounds like tensor calculus, which leads to, as Spivak calls it in his differential geometry tome, "The debauch of indicies."
