  Wikipedia is a popular web-based encyclopedia edited freely and
collaboratively by its users. In this paper we present an analysis of
Wikipedias in several languages as complex networks. The hyperlinks pointing
from one Wikipedia article to another are treated as directed links while the
articles represent the nodes of the network. We show that many network
characteristics are common to different language versions of Wikipedia, such as
their degree distributions, growth, topology, reciprocity, clustering,
assortativity, path lengths and triad significance profiles. These
regularities, found in the ensemble of Wikipedias in different languages and of
different sizes, point to the existence of a unique growth process. We also
compare Wikipedias to other previously studied networks.
