What is a set | Set theory

What is a set?

Set can be defined as the collection of well-defined object that’s all.
The meaning of ” well-defined” in set is those type of collection which is not depend on choice.Like collection of beautiful women in India. Which depend on choice only and different people has different different choice. So such collection is not a set.
Followings are some special set and their standard name
Which is in many book
N : for the set of natural numbers.
Z : for the set of integers.
Z+ : for the set of all positive integers.
Q : for the set of all rational number.
Q+ : for the set of all positive rational number.
R : for the set of all real numbers.
R+ : for the set of all positive real numbers.
C : for the set of all complex numbers.

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