Crisis is the situation of a complex system (family, economy, society) when the system functions poorly, an immediate decision is necessary, but the causes of the dysfunction are not known.

a) situation of a complex system – simple systems do not enter crises. We can speak about a crisis of moral values, an economical or political crisis, but not a motor crisis.

b) poor function. The system still functions, but does not break down.

c) an immediate decision is necessary to stop the further disintegration of the system.

d) the causes are so many, or unknown, that it is impossible to take a rational, informed decision to reverse the situation.

Crisis has several defining characteristics. Seeger, Sellnow, and Ulmer[2] say that crises have four defining characteristics that are "specific, unexpected, and non-routine events or series of events that [create] high levels of uncertainty and threat or perceived threat to an organization's high priority goals." Thus the first three characteristics are that the event is

1. unexpected (i.e., a surprise)

2. creates uncertainty

3. is seen as a threat to important goals

Venette[3] argues that "crisis is a process of transformation where the old system can no longer be maintained." Therefore the fourth defining quality is the need for change. If change is not needed, the event could more accurately be described as a failure.  (http://en.wikipedia.org/wiki/Crisis, Accessed on 19 February 2013)