Why is calligraphy an abstract art, but not an abstract art?

Writing itself is an abstraction, a tool made by human beings to understand and use the knowledge gained from this world. Many people refer to natural objects first, and then create characters according to other rules such as grammar. This concept is very abstract, so calligraphy, as an artistic method to express characters, belongs to the category of abstract art, which is an artistic style developed from the later period of western realistic painting and a modern artistic trend of thought starting from Cezanne. Mainly to explore the physical essence of color materials, in detail, this is a genre of style, called abstraction. On a large scale, it also belongs to abstract art, but calligraphy does not belong to abstraction.