7. We can say that a set is infinite if it is not finite.
8. The number of elements in a finite set is called the cardinal number/ cordinality of the set.
9. The universal set is denoted by 'u' or U. Theuniversal set is usually represented by
rectangles.
10. A is a subset of B if 'a' is an element of A implies that 'a' is also an element of B. This is
written as A ⊆ B if a ∈A → a ∈ B, where A, B are two sets.
11. Two sets, A and B are said to be equal if; every element in A belongs to B and every
element in B belongs to A.
12. A union B is written as A U B = {x : x ∈ A or x ∈ B}.
13. A intersection B is written as A ∩ B = {x : x ∈ A and x ∈ B}
14. The difference of two sets A, B is defined as A - B
A - B = {x : x ∈ A and x ∉ B}
15. Venn diagrams are a convenient way of showing operations between sets.