# bad formating of ff in math mode

I'm trying to write something like: $affinity(x)$, but in the PDF I see some small spacing between the two f's.

I tried $af{}firm(x)$ or $aff{}irm(x)$, but nothing works.

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In general math words should not be entered "undecorated" in TeX as they are typeset as separate letters, not as a word....which is why we use \mathit and the like. –  Yossi Farjoun Nov 27 '10 at 16:17

$\mathit{affinity}(x)$

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Thanks! that did it. –  Hagai Cibulski Nov 27 '10 at 14:03

How do you usually write maps, functions and operators in your math text? Italic as well?

Math operators are commonly written in upright letters, in contrary to variables which have italic shape. I would use \mathrm instead of \mathit or better

\DeclareMathOperator{\affinity}{affinity}


of amsmath, and write \affinity in the formulas. Here's a complete example, just compare:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\affinity}{affinity}
\begin{document}
$\affinity(x) \neq \mathit{affinity}(x) \neq y(x),$
$\max_f \lim_a af = a\cdot f$
\end{document}


Output:

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$affinity$ stands for the product of the variables a, f, f, i, …. Wordlike functions are usually written in an upright font, usually with \DeclareMathOperator:
\usepackage{amsopn}