  Persistence is an important characteristic of many complex systems in nature,
related to how long the system remains at a certain state before changing to a
different one. The study of complex systems' persistence involves different
definitions and uses different techniques, depending on whether short-term or
long-term persistence is considered. In this paper we discuss the most
important definitions, concepts, methods, literature and latest results on
persistence in complex systems. Firstly, the most used definitions of
persistence in short-term and long-term cases are presented. The most relevant
methods to characterize persistence are then discussed in both cases. A
complete literature review is also carried out. We also present and discuss
some relevant results on persistence, and give empirical evidence of
performance in different detailed case studies, for both short-term and
long-term persistence. A perspective on the future of persistence concludes the
work.
