How to insert LaTeX symbols? [duplicate]

Possible Duplicate:
How does one insert a backslash or a tilde into LaTeX?

I tried inserting symbols in latex. e.g.: \texttildelow

It didn't work. But symbols like \textasciitilde work.

I can't understand why some symbols work and others (the first one mentioned here) result in "undefined control sequence" error.

marked as duplicate by Werner, Torbjørn T., Joseph Wright♦Oct 2 '11 at 7:12

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1 Answer

these symbols need the textcomp package:

\documentclass{article}
\usepackage{textcomp}%

\begin{document}
\texttildelow

\textasciitilde
\end{document}