Here's why:

* Mass is a fundamental property of matter that measures its resistance to acceleration. It essentially tells us how much "stuff" something is made of.

* Matter occupies space, meaning it has volume.

* Matter has weight, which is the force of gravity acting on its mass.

While other characteristics like color, texture, and temperature can be useful in describing matter, they aren't fundamental to its definition.

So, anything that has mass is considered matter, whether it's a solid, liquid, gas, or even plasma.