tilde below a character

[akif]

As you know, \tilde{x} produces an x character with a tilde on top of
it. Now, I want an x with a tilde BELOW it, to represent a random
variable. How can I achieve this?

M. Akif YAZICI
PhD candidate @Bilkent University
Dept. of Electrical & Electronics Eng.
Office: EA132[BINLAB]
Tel: +90 312 290 2338

[Werner]

You could take a look at
http://www.ctan.org/tex-archive/info/symbols/comprehensive/
for a comprehensive list of LaTeX symbols. From this list, I see that
you could use
\usepackage{wsuipa}
\diunder[\undertilde|a]
See the documentation, available from http://tug.ctan.org/cgi-bin/ctanPackageInformation.py?id=wsuipa
, for more information. If you have require an 'extensible' tilde
under a number of characters,
\usepackage{undertilde}
\utilde{abc}
See the documentation, available from
http://tug.ctan.org/cgi-bin/ctanPackageInformation.py?id=undertilde ,
for more information.

Werner