1. A set is a collection of well-defined objects or elements, characterized by clear and unambiguous criteria for membership.

2. Elements are the individual objects within a set, clearly defined without ambiguity.

3. Sets are described in the following ways
a) Verbal method (Describing sets using words)

b) Listing method

i) Partial listing method (Listing some elements followed by ellipses (…).

ii) Complete listing method (Listing all elements explicitly.
c) Set-builder method

4. The Greek symbol ∈ is used to denote membership in a set (e.g., a ∈ A), while ∉ indicates non-membership (e.g., b ∉ A).

5. Sets are usually denoted by capital letters (e.g., A, B, C), and their elements are listed within curly braces $(e.g., \{a, b, c\})$.