Meaning of COMPLEXITY in English
/ kəmˈpleksəti; NAmE / noun
[ U ] the state of being formed of many parts; the state of being difficult to understand :
the increasing complexity of modern telecommunication systems
I was astonished by the size and complexity of the problem.
complexities [ pl. ] the features of a problem or situation that are difficult to understand :
the complexities of the system
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005