Which bamboo, grass and wood fields are different?

"Tian" in "bamboo, wood, field and grass" is not one kind, and "Tian" refers to fields, not crops. "Bamboo, wood and grass" belong to the same category, referring to plants, crops and living things. These three are all plants, but they are not the same. They have life, and the fields have no life, so they belong to inorganic things.

There are basically two classification methods:

One is manual classification, which classifies things according to their external characteristics. For convenience, people classify all kinds of goods, display them at different counters and sell them in different stores. This classification method can be called external classification.

Another classification method is to classify things according to their essential characteristics. A whale living in the ocean is like a fish, but it doesn't belong to a fish. It is a viviparous mammal. It has no scales on its body, breathes with its lungs and has no gills. It has the characteristics of a mammal. It is an essential classification to classify whales as mammals. This is called essential classification.