.ac (short for academia) is a second level domain for academic establishments, such as universities, colleges and research institutes.[1] Many countries use .edu for the same purpose, for example .edu.au in Australia, .edu.my in Malaysia. Still other countries (examples include France, the Netherlands and Switzerland), do not maintain a second level domain specifically for academic institutions. Rather, each institution will have its own second-level domain (such as sorbonne.fr for the Sorbonne, or tum.de for the Technical University of Munich).
Though similar, there can be a slight distinction between .edu and .ac. For example, in 2006 China announced that .edu would be used (with .cn) as the second-level domain for educational institutions, while .ac would be used for research institutions. [2]