Science is a direction of research that allows to determine the patterns that answer the question "What will happen next?"
Examples of such directions: physics, chemistry, biology, psychology, sociology, economics.
Direction of research may not be a science if they do not answer the question "What will happen next?", But only answer the question "What happened before?" or "What's happening now?"
Examples of such directions: history, archeology, anthropology, geography.
For such a classification, it is necessary to define the categories: "it was before", "is happening now" and "will be further", that is, to define the concepts of "past", "present" and "future". In order not to deviate from the topic, I will stand on the fact that these concepts are given to us a priori.
In this definition of science, there is no sign of the creation of a knowledge system. To describe this feature, it is necessary to define the concepts of "system" and "knowledge", and this is a very time-consuming process. For reasons of unwillingness to deviate from the topic, these concepts will not be described here. Let the attribute of the creation of a knowledge system refer to research. If a system of knowledge is created, then this is research, and if it is not created, then this is an observation.
Perhaps, someone will see in this definition of science signs of discrimination. If we use the reliability of the statement that science should be impartial, then such speculation will only emphasize the accuracy of the criterion for defining science, and the groundlessness of such accusations.
A subject is a science in which all laws have already been investigated, that is, there is nothing to explore. Examples of such directions of scientific research known to me: logic and descriptive geometry.
A profession is an activity aimed at creating of some kind of a product, such as a goods or services. Examples of such directions: agriculture, industry, medicine, architecture, music, literature.
Any professional activity can be called an art.