Measure of algorithm resource usage.

Measure of algorithm efficiency, speed.

Study of computational problem difficulty.

Memory usage of an algorithm.

Quantification of system's structural intricacy.

In theoretical computer science, circuit complexity is a branch of computational complexity theory in which Boolean functions are classified according to the size or depth of the Boolean circuits that compute them.

(biology, pseudoscience) The proposition that complex organs such as eyes and flagella must have started existing in their current form; i.e., that they cannot have evolved from previous, less complex stages.