Complexity and complicacy are two words that are often used interchangeably, but they actually have different meanings. Complexity refers to the number of elements or parts that make up a system or structure. It can also refer to the difficulty of understanding a concept or system. Complicacy, on the other hand, is the degree of intricacy or intricateness of a system or structure. It is usually used to describe the degree of difficulty in understanding a concept or system. While complexity and complicacy are related, they are not the same.