In linguistics, the topic (or theme) is informally what is being talked about, and the comment (rheme or focus) is what is being said about the topic. Although this general nature of topic-comment dichotomy is generally accepted, anything beyond that is a matter of great controversy.
The distinction was probably first suggested by Henri Weil in 1844.
Georg von der Gabelentz distinguished psychological subject (roughly topic) and
psychological object (roughly focus). In the Prague school, the
dichotomy has been studied mainly by Vilém Mathesius, Jan Firbas, František Daneš, Petr Sgall and Eva Hajičová. They were concerned
mainly by its relation to intonation and word-order. The work of
Michael Halliday in the 1960s is probably responsible for bringing the ideas to Generative Linguistics.
Note that in some categorizations, topic refers only to the contrastive theme and comment to the noncontrastive theme + rheme.
Realization of topic/comment
Different languages mark topics in different ways. Distinct intonation and word-order are the most common means. The tendency to place topicalized constituents sentence-initially (topic fronting) is widespread. Again, linguists disagree on many details.
- English: intonation is the primary means, although word order (e.g., fronting of contrasted topics: Kim, I like.) and other syntactic (passivisation, clefting) or lexical means ("As for...", "Regarding...") are also employed.
- Japanese: topic is marked with a special clitic postposition (は, wa).
- So called free-word order languages (e.g. Russian, Czech, to a certain extent Chinese or German) use word-order as the primary means. Usually topic precedes focus. However, for example in Czech, both orders are possible. The order with comment sentence-initial is referred as subjective (V. Mathesius' term, as opposed to objective) and expresses certain emotional involvement. The two orders are distinguished by intonation.
- Georg von der Gabelentz, Die Sprachwissenschaft, ihre Aufgaben, Methoden und bisherigen Ergebnisse T.O. Weigel Nachfolger, 1891
- Charles F. Hockett, A Course in Modern Linguistics. The Macmillan Company: New York 1958. (pp. 191-208)
- Vilém Mathesius, A Functional Analysis of Present Day English on a General Linguistic Basis. edited by Josef Vachek, translated by Libuše Dušková. The Hague - Paris: Mouton 1975.
- Nirit Kadmon, Pragmatics Blackwell Publishers. Blackwell Publishers 2001
- Henri Weil, De l'ordre des mots dans les langues anciennes comparees aux langues modernes: question de grammaire general. 1844. Published in English as The order of words in the ancient languages compared with that of the modern languages. 1887