Question

What is intutive definition of an element

Answer 1

Intuitively, a “set” is a collection of things, called itselements, or members. To say that x is an element of S, we write x ∈ S . Other ways of saying this: “x belongs to S”, “S contains x”, ”x is in S”,
Notice that we don't actuallydefine the term “set”.
A set with exactly one element is called a singleton.