How do we Define things? Few examples on Medicinal Plants and Sleep

It was discussed that Phyllanthus is a medicinal plant for Jaundice. The question was asked by GN which plant is non-medicinal?

We discussed all plants are medicinal. There was the point some plants are toxic , but Rahul pointed many painkillers are actually toxins. Even snake venom can be used as drugs or antidote.
Further, it was discussed that Phyllanthus is a used for studying sleep studies.
How do we define sleep?

How do we say plants are not sleeping when their leaves are open and waking when they close their leaves.

When we touch Mimosa they close the leaves do we say it sleeps on touching?
So it is very complicated to use sleep terminology, but closing and opening of leaves, we can call it as a biological rhythm.