👉 In mathematics and logic, a coeternal (or coeternal) is an object that can be considered as both a first and second class in some mathematical structure or system. It is often used to describe the relationship between two elements of a set, where one element is considered to be "co-eternal" with respect to another. In the context of sets, coets are commonly used for defining properties such as being a subset of another set, having an equal number of elements,