Question

What is science? why is science divided into three parts?

Answer 1

Science is the study of each and every object on earth. It is divided into three based on what it is about

Answer 2

Science is the field of giving rigorous answers, but ironically the definition of "science" is itself not rigorous.

Science is:

Processes for creating models for reliable prediction and control of the natural world;

Models created using those processes; and  

Application of those models.