Quantity: quantity, weight, length, area, volume …
Shape: rectangle, square, triangle, trapezoid, circle, cuboid, cube, cylinder, sphere …
Logic: judgment, reasoning, probability …
Three characteristics of elements in a set:
1, element certainty;
2. Mutual anisotropy of elements;
3. Description of element disorder:
(1) For a given set, the elements in the set are certain, and any object is either an element of the given set or not.
(2) In any given set, any two elements are different objects. When the same object is contained in a collection, it is only an element.
(3) The elements in the set are equal and have no order. So to judge whether two sets are the same, we only need to compare whether their elements are the same, and we don't need to examine whether the arrangement order is the same.
(4) The three characteristics of set elements make the set itself deterministic and holistic.