There were a couple of years when I was tremendously confused about pragmatics and information structure. I learned a lot from reading Knud Lambrecht’s 1994 book Information Structure and Sentence Form. And one of the most useful things I learned was that people use the word “topic” to mean several different things, some of which are mutually exclusive.
Here are the words and definitions that Lambrecht used for these concepts, along with some commentary:
- topic referent. “A referent is interpreted as the topic of a proposition if in a given situation the proposition is construed as being about this referent.”
- topic expression (also known as topic NP, topic pronoun, topic phrase, topic constituent). “A constituent is a topic expression if the proposition expressed by the clause with which it is associated is pragmatically construed as being about the referent of this constituent.” Topic expressions are what the speaker/author produces; topic referents are the actual topics that the topic expressions refer to.
- topic-announcing expression. An expression used to announce a topic shift or promote a referent to topic status. Topic expressions simply signal what the sentence is about, while topic-announcing expressions mark a change in the topic referent.
- subject. A syntactic role describing an argument of a verb, often referring to the agent of an action. “Subjects are unmarked topics.” In traditional rhetoric, subject (also called psychological subject) meant something very similar to Lambrecht’s topic referent: “The thing which the proposition expressed by the sentence is about.”
- agent. A semantic role describing an active participant in an action. Agents are often topic referents.
- theme. The element which comes first in the sentence. A Prague School term, which is also called “topic” by some. Lambrecht’s topic expressions often come first in a sentence.
- old information. Presupposed propositions. All topic referents must be in the presupposition, but not all referents in the presupposition are topics.
- topicalization (also called fronting). A syntactic construction where a noun phrase that is normally integrated into the argument structure of a sentence instead appears at the beginning of the sentence, before the subject. Often used as a topic-announcing expression, but also for contrastive focus.
- left-dislocation (also called left-detachment). Like topicalization, but with a coreferential pronoun integrated into the sentence. Often used as a topic-announcing expression, but also for contrastive focus.
- “Chinese-style” topic. Where the normal sentence structure has a place for topic-announcing constituents that are not necessarily arguments of the verb. Lambrecht’s topic expressions include these and others.
- discourse topic. What the entire discourse is about. Lambrecht’s topic referent typically covers only a particular sentence, not the entire discourse.
- topic/comment. One of Lambrecht’s possible sentence types, discussed in more detail in Chapter 5. Necessarily includes a topic expression.
- antitopic (also called right-dislocation and right-detachment). A construction similar to left-dislocation, but where the noun phrase appears at the end of the sentence. Lambrecht analyzes antitopics as unaccented topic-announcing expressions.
- contrastive topic. A construction that contrasts two propositions based on their topic referents. Typically has two accented topic expressions.
- focus. “The semantic component of a pragmatically structured proposition whereby the assertion differs from the presupposition.” Topic expressions and focus expressions are both sometimes accented, and it’s hard to tell whether a particular accented constituent is a topic expression or a focus expression.
Hope this helps!