Creating your own diacritics

Question

How does one create one's own diacritics? To give a concrete example, I want to be able to typeset something that looks like

ä

but has three dots above the letter. I'm looking for an answer that looks comparably nice to existing diacritics, if possible.

Answer 1

Another option is to use the accents package:

\documentclass{article}
\usepackage{accents}

\begin{document}

$\dddot{\mathbf{a}}\quad\ddddot{\mathbf{a}}$

\end{document}

Answer 2

In amsmath this is already defined: \dddot{a}. You can even have 4 dots: \ddddot{a}. (Works in math mode only though.)