Editing Complexity (section)

{{Short description|Properties of systems that cannot be simply described or modeled}}
{{About||the use in computer science|Computational complexity|other uses|Complexity (disambiguation)}}

'''Complexity''' characterizes the behavior of a [[system]] or [[model]] whose components interact in multiple ways and follow local rules, leading to [[Nonlinear system|non-linearity]], [[randomness]], [[Dynamical system|collective dynamics]], [[hierarchy]], and [[emergence]].<ref name="steven">{{cite book
| last = Johnson
| first = Steven
| title = Emergence: The Connected Lives of Ants, Brains, Cities
| publisher = Scribner
| year = 2001
| location = New York
| url = https://books.google.com/books?id=Au_tLkCwExQC
| page = 19
| isbn = 978-3411040742}}
</ref><ref>{{Cite web |title=What is complex systems science? {{!}} Santa Fe Institute |url=https://www.santafe.edu//what-is-complex-systems-science |access-date=2022-04-17 |website=www.santafe.edu |language=en |archive-date=2022-04-14 |archive-url=https://web.archive.org/web/20220414202627/https://santafe.edu/what-is-complex-systems-science |url-status=dead }}</ref>

The term is generally used to characterize something with many parts where those parts interact with each other in multiple ways, culminating in a higher order of emergence greater than the sum of its parts. The study of these complex linkages at various scales is the main goal of [[complex systems theory]].

The intuitive criterion of complexity can be formulated as follows: a system would be more complex if more parts could be distinguished, and if more connections between them existed.<ref>Heylighen, Francis (1999). ''The Growth of Structural and Functional Complexity during Evolution'', in; F. Heylighen, J. Bollen & A. Riegler (Eds.) The Evolution of Complexity. (Kluwer Academic, Dordrecht): 17–44.</ref>

{{As of|2010}}, a number of approaches to characterizing complexity have been used in [[science]]; Zayed ''et al.''<ref>
J. M. Zayed, N. Nouvel, U. Rauwald, O. A. Scherman. ''Chemical Complexity – supramolecular self-assembly of synthetic and biological building blocks in water''. Chemical Society Reviews, 2010, 39, 2806–2816 http://pubs.rsc.org/en/Content/ArticleLanding/2010/CS/b922348g
</ref>
reflect many of these. [[Neil F. Johnson|Neil Johnson]] states that "even among scientists, there is no unique definition of complexity – and the scientific notion has traditionally been conveyed using particular examples..."  Ultimately Johnson adopts the definition of "complexity science" as "the study of the phenomena which emerge from a collection of interacting objects".<ref name="Neil Johnson">{{cite book
 |last         = Johnson
 |first        = Neil F.
 |title        = Simply complexity: A clear guide to complexity theory
 |publisher    = Oneworld Publications
 |year         = 2009
 |chapter      = Chapter 1: Two's company, three is complexity
 |page         = 3
 |chapter-url          = http://www.uvm.edu/rsenr/nr385se/readings/complexity.pdf
 |isbn         = 978-1780740492
 |access-date  = 2013-06-29
 |archive-url  = https://web.archive.org/web/20151211064454/http://www.uvm.edu/rsenr/nr385se/readings/complexity.pdf
 |archive-date = 2015-12-11
 |url-status     = dead
}}</ref>