I was looking for the definition of the “subject” in a syntactic sense. What does it mean the “subject” of a clause? The subject of the clause is not the person who performances the action because that person is the agent and the agent is not always the subject of the clause ─as occurs in the passive constructions. Despite nouns are the most common subjects, we cannot define the subject as a noun because other word classes can also be subjects, such as verbs, pronouns or even adjectives. What is then the “subject” of a clause? I think that we can only define the “subject” by its function in the clause: the subject is that what is being said of something. We cannot say anything more about the subject, and we cannot do that because the “subject” is a pure formal construction. If we want to know the meaning of the “subject” beyond that, we must introduce into it some kind of content. So, we can only know the meaning of this or that “subject”, but not the “subject” in general.