When you can observe something's characteristics, they are called physical traits. These are the things you can see, hear, smell.
A property, or maybe something specifically, an empirical
A characteristic of something you are able to observe is that you are actually able to see it. It is also imperative that you would be able to notice changes in its appearance or behavior.
It is its property.
Rate of Erosion
I believe we only observe.
rate of erosion
Getting data
inferring something
Yes. Specifically, the sense of touch.
A characteristic is, something that a person does for a living.
I agree.
something that observe light