What Is Microscope Simple Definition?
A microscope is a tool that makes very small things look bigger so we can see details that are hard or impossible to see with just our eyes.
For example, if you look at a drop of pond water with your eyes, it may look clear. Under a microscope, you might see tiny living organisms moving around. The microscope helps magnify the image, which means it enlarges what you are looking at.
A simple definition would be:

A microscope is an instrument used to magnify tiny objects so they can be seen more clearly.

Microscopes are commonly used in science classrooms, hospitals, laboratories, and research centers. People use them to study things like cells, bacteria, plant parts, blood samples, insects, and tiny structures in materials.

Most basic school microscopes use lenses and light. The lenses bend light to make the object appear larger. This kind is usually called a light microscope or compound microscope.

A microscope is useful because many important things in nature are too small to see normally. Cells, for example, are the basic units of living things, but most cells are so tiny that we need a microscope to study them.
In short, a microscope helps us see the small world that is hidden from the naked eye.