The systematic study of the physical world and its phenomena through observation, experimentation, and the development of testable explanations.

Here's why:

* Systematic study: Natural sciences employ a structured approach to investigating the world, utilizing scientific methods.

* Physical world: The focus is on understanding the universe, from the smallest particles to the vast cosmos.

* Observation and experimentation: Scientists gather data through careful observation and controlled experiments.

* Testable explanations: The goal is to develop theories and models that can be tested and potentially falsified, leading to an ever-evolving understanding of the natural world.

Here's a breakdown of some common natural sciences:

* Biology: The study of life and living organisms.

* Chemistry: The study of matter and its properties.

* Physics: The study of the fundamental laws of the universe.

* Astronomy: The study of celestial objects and phenomena.

* Geology: The study of Earth's composition, structure, and history.

Let me know if you'd like more details on any of these branches!