Essential complexity is a way to measure how “structured” something is. Think of structure like the pattern on a rug where all the pieces fit together and make a picture, or a pyramid where all the stones are organized and built up in a certain way. When something is “structured”, it has a system or pattern that makes it clear how it works. Essential complexity is a way to measure this structure. Numerical measures of essential complexity are numbers that show how “structured” something is. For example, if something has a lot of structure, its essential complexity number will be high. If something does not have much structure, its essential complexity number will be low. So, it’s a way to measure how “structured” something is.