• Subjects are one of the five types of clause element. The others are: verb phrases, objects, complements and adverbials.
The clause elements are functional (as opposed to formal) categories. In other words, they are defined primarily in terms of their position in a clause, their mobility and whether or not they are obligatory. Formal (or “structural”) factors enter into their definitions, however: for example, in defining adverbials, it is necessary to mention that they can “fulfilled” by adverb phrases, prepositional phrases, or clauses. [See also the entry: “grammatical form and function.”]
• There are four groups of characteristic features of subjects: those concerning form, position, syntactic function, and semantic properties.
♦ the form of subjects—
The subject of a clause is almost always either a noun phrase ( That beautiful woman is Harry’s wife) or a noun clause ( Why she married him is a mystery).
♦ the syntactic function of subjects:
i. the position of subjects: The normal position of a subject is before the verb phrase in a statement ( Harry smokes expensive cigars.) and after the “operator” in questions (Does Harry smoke expensive cigars?). There is an important exception to this rule in the case of wh- questions in which the “wh- element” is the subject: ( What makes Harry behave that way?)
ii. the obligatory status of subjects: subjects are required in all finite clauses except for “imperative” clauses.
iii. subjects act as determinants of “number” and “person” of verbs, complements and pronouns: For example, Harry is my friend, but, Harry and Sara are my friends.
iv. subjects and the passive voice: if an active clause is made passive, then the direct or indirect object of the active clause becomes the subject of the passive clause and the subject of the active clause is either omitted or is expressed in a “by-agent phrase.”
♦ the semantic properties of subjects
i. Typically, in an active clause the subject identifies the agent (the person or thing that acts rather than the one that is “affected”)
• For example, in “Harry smokes cigars,” the subject Harry is the agent (i.e. the person or thing that “acts” and the object, cigars refers to the “affected entity” (the person or thing toward which the action is directed). Although the agentive subject is typical, subjects play many other semantic roles including that “prop it subjects” in sentences such as It’s raining.
ii. Normally the subject identifies the “theme” of a clause (as opposed to the “focus”)
The “theme”of a clause provides information that is regarded as “given”; the “focus” provides new information. Consider the following short dialog: Tom: “Where's Harry?” Dick: “Harry is in his office?” Tom already knows that Dick’s reply is going to be about Harry so that information is appropriately placed in the subject position.