Complexity characterises the behaviour of a system or model whose components interact in multiple ways and follow local rules, meaning there is no reasonable higher instruction to define the various possible interactions.The stem of the word "complexity" - complex - combines the Latin roots com (meaning "together") and plex (meaning "woven").In Weaver's view, disorganized complexity results from the particular system having a very large number of parts, say millions of parts, or many more.Though the interactions of the parts in a "disorganized complexity" situation can be seen as largely random, the properties of the system as a whole can be understood by using probability and statistical methods.
Organized complexity, in Weaver's view, resides in nothing else than the non-random, or correlated, interaction between the parts.
There are generally rules which can be invoked to explain the origin of complexity in a given system.
The source of disorganized complexity is the large number of parts in the system of interest, and the lack of correlation between elements in the system. Complexity of an object or system is a relative property.
Many definitions tend to postulate or assume that complexity expresses a condition of numerous elements in a system and numerous forms of relationships among the elements.
However, what one sees as complex and what one sees as simple is relative and changes with time.