Complexity (noun)

1. The state or quality of being complicated or composed of interconnected parts.
2. The degree to which something is difficult to understand or explain.
3. The number of interrelated elements in a system or structure.

Origin:

Derived from the latin word 'complexitas' meaning 'a combination'.

Examples:

1. The complexity of the system made it difficult to understand.
2. The complexity of the tax code is a major challenge for many people.
3. The complexity of the situation required careful consideration.