# Complexity

There are different senses of**complexity**:

- In information processing, complexity is a measure of the total number of properties transmitted by an object and detected by an observer. Such a collection of properties is often referred to as a state.
- In computer science, the study of how much time and memory a computer algorithm may take is the field of
**computational complexity theory**. **Complexity**is often used as a shorthand for the field that developed in the late 1980s around the use of mathematical and computational modeling of biological, economic and technological systems known as "**complex systems**" (sometimes complex adaptive systems).- In the sense of how complicated a problem is from the perspective of the person trying to solve it, limits of complexity are measured using a term from cognitive psychology, namely the hrair limit.
- In mathematics, Krohn-Rhodes complexity is an important topic in the study of finite semigroups.