Category. Designations
- Any amount: Category, B, C, M, ….
2. Spellings and definitions
B. Relations between sets
* The notation A ⊆ B is also equivalent
C. Operations with sets
D. Laws of set algebra
Category, B, Let C be subsets of a basic set E.
duality principle: If one exchanges the links ∩ and U and at the same time Ø and E with each other in a law of set algebra, so there is again a law of set algebra.
E. Classification (Disassembly) a lot
There is a class division, when a set is broken down into subsets, so that
(1) each subset contains at least one element,
(2) the intersection of any two subsets is empty,
(3) the union of all subsets gives the original set.