n linguistics, the topic, or theme, of a sentence is what is being talked about, and the comment (rheme or focus) is what is being said about the topic. This division into old vs. new content is called information structure. It is generally agreed that clauses are divided into topic vs. comment, but in certain cases the boundary between them depends on which specific grammatical theory is being used to analyze the sentence.
Topic, which is defined by pragmatic considerations, is a distinct concept from grammatical subject, which is defined by syntax. In any given sentence these may be the same, but they need not be. For example, in the sentence "As for the little girl, the dog bit her", the subject is "the dog" but the topic is "the little girl".
Topic and subject are also distinct concepts from agent (or actor)—the "doer", which is defined by semantics. In English clauses with a verb in the passive voice, for instance, the topic is typically the subject, while the agent may be omitted or may follow the preposition by. For example, in the sentence "The little girl was bitten by the dog", "the little girl" is the subject and the topic, but "the dog" is the agent.
In some languages, word order and other syntactic phenomena are determined largely by the topic–comment (theme–rheme) structure. These languages are sometimes referred to as topic-prominent languages. Korean and Japanese are often given as examples of this.
Contents
1 Definitions and examples
2 Realization of topic–comment
2.1 In English
2.2 In other languages
3 Practical applications
4 History
5 See also
6 References
7 Further reading
8 External links
Definitions and examples
The sentence- or clause-level "topic", or "theme", can be defined in a number of different ways. Among the most common are
the phrase in a clause that the rest of the clause is understood to be about,
a special position in a clause (often at the right or left-edge of the clause) where topics typically appear.
In an ordinary English clause, the subject is normally the same as the topic/theme (example 1), even in the passive voice (where the subject is a patient, not an agent: example 2):
The dog bit the little girl.
The little girl was bitten by the dog.
These clauses have different topics: the first is about the dog, and the second about the little girl.
In English it is also possible to use other sentence structures to show the topic of the sentence, as in the following:
