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{{Short description|Terms describing sentence structure in linguistics}}
{{About|the topic of a sentence|the topic of a discourse|Discourse topic|theme (also called topic) in generative grammar|Theta role|theme in semantics|Thematic relation}}
{{More citations needed|date=October 2011}}
{{Use dmy dates|date=June 2015}}
{{Grammatical categories}}

In [[linguistics]], the '''topic''', or '''theme''', of a [[Sentence (linguistics)|sentence]] is what is being talked about, and the '''comment''' ('''rheme''' or '''[[Focus (linguistics)|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 [[clause]]s 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.

The topic of a sentence is distinct from the grammatical [[Subject (grammar)|subject]].  The topic is defined by [[Pragmatics|pragmatic]] considerations, that is, the [[wiktionary:context|context]] that provides meaning. The grammatical subject is defined by [[Syntax (logic)|syntax]]. In any given sentence the topic and grammatical subject 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 being what is being talked about and the [[Subject–object–verb word order|subject]] being what is doing the action can, also, be distinct concepts from the concept [[Agent (grammar)|agent]] (or actor)—the "doer", which is defined by [[semantics]], that is, by the contextual meaning of the sentence in the paragraph. 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 [[Syntax|syntactic phenomena]] are determined largely by the topic–comment (theme–rheme) structure. These languages are sometimes referred to as [[topic-prominent language]]s. Korean and Japanese are often given as examples of this.

== 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:
*''As for the little girl'', the dog bit her.
*''It'' was the little girl ''that the dog bit.''

The case of [[Expletive (linguistics)|expletives]] is sometimes rather complex. Consider sentences with expletives (meaningless subjects), like:

*It is raining.
*There is some room in this house.
*There are two days in the year in which the day and the night are equal in length.

In these examples the syntactic subject position (to the left of the verb) is manned by the meaningless expletive ("it" or "there"), whose sole purpose is satisfying the [[extended projection principle]], and is nevertheless necessary. In these sentences the topic is never the subject, but is determined [[Pragmatics|pragmatically]]. In all these cases, the whole sentence refers to the comment part.<ref>Michael Gotze, Stephanie Dipper, and Stavros Skopeteas. 2007. Information Structure in Cross-Linguistic Corpora: Annotation Guidelines for Phonology, Morphology, Syntax, Semantics, and Information Structure. Interdisciplinary Studies on Information Structure (ISIS), Working papers of the SFB 632, Vol. 7.</ref>

The relation between topic/theme and comment/rheme/focus should not be confused with the topic-comment relation in [[Rhetorical structure theory|Rhetorical Structure Theory]]-Discourse [[Treebank]] (RST-DT corpus) where it is defined as "a general statement or topic of discussion is introduced, after which a specific remark is made on the statement or topic". For example: "[As far as the pound goes,] [some traders say a slide toward support at 1.5500 may be a favorable development for the dollar this week.]"<ref>L. Carlson and D. Marcu, “Discourse tagging reference manual,” ISI Technical Report ISI-TR-545, vol. 54, 2001.</ref><ref>L. Ermakova and J. Mothe. 2016. Document re-ranking based on topic-comment structure. In X IEEE International Conference RCIS, Grenoble, France, June 1–3, 2016. 1–10.</ref>

== 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. Topic fronting refers to placing the topic at the beginning
of a clause regardless of whether it is marked or not.<ref>D. Bring, Topic and Comment. Cambridge University Press, 2011, three
entries for: Patrick Colm Hogan (ed.) The Cambridge Encyclopedia of
the Language Sciences. Cambridge: Cambridge University Press.</ref> Again, linguists disagree on many details.

Languages often show different kinds of grammar for sentences that introduce new topics and those that continue discussing previously established topics.

When a sentence continues discussing a previously established topic, it is likely to use pronouns to refer to the topic. Such topics tend to be subjects.  In many languages, pronouns referring to previously established topics will show [[pro-drop]].

=== In English ===
In English the topic/theme comes first in the clause, and is typically marked out by intonation as well.<ref>MAK Halliday (1994). ''An introduction to functional grammar'', 2nd ed., Hodder Arnold: London, p. 37</ref>

English is quite capable of using a topic-prominent formulation instead of a subject-prominent formulation when context makes it desirable for one reason or another. A typical pattern for doing so is opening with [[wikt:Thesaurus:about|a class of prepositions such as: ''as for'', ''as regards'', ''regarding'', ''concerning'', ''respecting'', ''on'', ''re'', and others]]. [[Pedagogy|Pedagogically]] or [[rhetorical modes#Exposition|expositorily]] this approach has value especially when the speaker knows that they need to [[attention management|lead the listener's attention]] from one topic to another in a deftly efficient manner, sometimes actively avoiding misplacement of the focus of attention from moment to moment. But whereas topic-prominent languages might use this approach by default or obligately, in subject-prominent ones such as English it is merely an option that often is not invoked.

=== In other languages===
{{Unreferenced section|date=October 2016}}
* In [[Japanese language|Japanese]] and [[Korean language|Korean]], the topic is usually marked with a [[postposition]] such as {{Nihongo||は|-wa}} or 는/은, ''-(n)eun'' respectively, which comes after the noun or phrase that is being topicalized.
* In [[Côte d'Ivoire]] [[French language|French]], the topic is marked by the postposition "là". The topic can be, but is not necessarily a noun or a nominal group, for example: « Voiture-là est jolie deh » ("That car is pretty"); « Aujourd'hui-là il fait chaud » ("It's hot on that day"); « Pour toi-là n'est pas comme pour moi hein » ("For you it's not the same as for me, huh"); and « Nous qui sommes ici-là, on attend ça seulement » ("We who are here, we are waiting for that only").
* So-called [[free word order]] languages such as [[Russian language|Russian]], [[Czech language|Czech]], and to some certain extent [[Chinese language|Chinese]] and [[German language|German]], use word order as the primary means, and the topic usually precedes the focus. For example, in some [[Slavic languages]] such as Czech and Russian, both orders are possible. The order with the comment sentence-initial is referred to as ''subjective'' ([[Vilém Mathesius]] invented the term and opposed it to ''objective'') and expresses certain emotional involvement.  The two orders are distinguished by intonation.
* In [[Modern Hebrew]], a topic may follow its comment. For example, the syntactic subject of this sentence is an expletive זה ("ze", lit. "this"):
{{fs interlinear|lang=he|indent=3
| זה מאד מענין הספר הזה
| ze meʾod meʿanyen ha-sefer ha-ze
| this very interesting book this
| "This book is very interesting."}}
* In [[American Sign Language#Topic and main clauses|American Sign Language]], a topic can be declared at the beginning of a sentence (indicated by raised eyebrows and head tilt) describing the referent, and the rest of the sentence describes what happens to that referent.

== Practical applications ==
The main application of the topic-comment structure is in the domain of speech technology, especially the design of embodied conversational agents (intonational focus assignment, relation between information structure and posture and gesture).<ref>Cassell, Justine, ed. Embodied conversational agents. MIT press, 2000.</ref> There were some attempts to apply the theory of topic/comment for information retrieval<ref>A. Bouchachia and R. Mittermeir, “A neural cascade architecture for
document retrieval,” in Neural Networks, 2003. Proceedings of the International Joint Conference on, vol. 3. IEEE, 2003, pp. 1915–1920.</ref> and automatic summarization.<ref>L. Ermakova, J. Mothe, A. Firsov. A Metric for Sentence Ordering Assessment Based on Topic-Comment.
Structure, in ACM SIGIR, Tokyo, Japan, 07/08/2017-11/08/2017</ref>

==History==
The distinction between subject and topic was probably first suggested by [[Henri Weil]] in 1844.<ref>H. Weil, De l’ordre des mots dans les langues anciennes compares aux
langues modernes: question de grammaire gnrale. Joubert, 1844.</ref> He established the
connection between [[information structure]] and word order. [[Georg von der Gabelentz]] distinguished '''psychological subject''' (roughly topic) and '''psychological object''' (roughly focus). In the [[Prague school]], the dichotomy, termed '''topic–focus articulation''', has been studied mainly by [[Vilém Mathesius]],<ref>V. Mathesius and J. Vachek, A Functional Analysis of Present Day
English on a General Linguistic Basis, ser. Janua linguarum : Series
practica / Ianua linguarum / Series practica. Mouton, 1975.</ref> [[Jan Firbas]], [[František Daneš]], [[Petr Sgall]] and [[Eva Hajičová]]. They have been concerned mainly by its relation to intonation and word-order. Mathesius also pointed out that the topic does not provide new information but connects the sentence to the context. The work of [[Michael Halliday]] in the 1960s is responsible for developing linguistic science through his [[systemic functional linguistics]] model for English.<ref>M.A.K.Halliday, An Introduction to Functional Grammar, 2nd ed.
London: Arnold, 1994.</ref>

==See also==
*[[Focus (linguistics)]]
*[[Predicate (grammar)]]
*[[Metafunctions#Textual function|Textual function (systemic functional linguistics)]]
*[[Thematic equative]]
*[[Topicalization]]
*[[Topic marker]]
*[[Topic-prominent language]]

==References==
{{reflist}}

==Further reading==
{{refbegin|30em}}
* [[Talmy Givón|Givón, Talmy]]. 1983a. ''[[Topic continuity in discourse]]: A quantitative cross-language study.'' Amsterdam: Arshdeep Singh.
* [[Eva Hajičová|Hajičová, Eva]], [[Barbara Partee|Partee, Barbara H.]], [[Petr Sgall|Sgall, Petr]]. 1998. ''Topic–Focus Articulation, Tripartite Structures, and Semantic Content.'' Studies in Linguistics and Philosophy 71. Dordrecht: Kluwer. (ix + 216 pp.) [https://archive.today/20050428002646/http://www1.cuni.cz/~peregrin/mybibl/HTMLTxt/434.htm review]
* Halliday, Michael A. K. 1967–68. "Notes on transitivity and theme in English" (Part 1–3). ''Journal of Linguistics'', 3 (1). 37–81; 3 (2). 199–244; 4(2). 179–215. 
* Halliday, Michael A. K. (1970). "Language structure and language function." In J. Lyons (Ed.), ''New Horizons in Linguistics''. Harmondsworth: Penguin, 140–65.  
* [[Charles F. Hockett|Hockett, Charles F.]] 1958. ''[http://krishikosh.egranth.ac.in/bitstream/1/20411/1/46174.pdf A Course in Modern Linguistics]''. New York: The Macmillan Company. (pp.&nbsp;191–208)
* [[Vilém Mathesius|Mathesius, Vilém]]. 1975. ''A Functional Analysis of Present Day English on a General Linguistic Basis''. edited by [[Josef Vachek]], translated by Libuše Dušková. The Hague – Paris: Mouton.
* Kadmon, Nirit. 2001. ''Pragmatics Blackwell Publishers''. Blackwell Publishers.
* Lambrecht, Knud. 1994. ''Information structure and sentence form.'' Cambridge: Cambridge University Press.
* Li, Charles N., Thompson, Sandra A. 1976. ''Subject and Topic: A New Typology of Languages'', in: Li, Charles N. (ed.) Subject and Topic, New York/San Francisco/London: Academic Press, 457–90.
* Payne, Thomas E.  1997.  ''[https://books.google.com/books?id=LC3DfjWfCiwC Describing morphosyntax: A guide for field linguists].''  Cambridge: Cambridge University Press.
* [[Georg von der Gabelentz|Von der Gabelentz, Georg]]. 1891.  ''Die Sprachwissenschaft, ihre Aufgaben, Methoden und bisherigen Ergebnisse.'' Leipzig: T.O. Weigel Nachfolger.
* [[Henri Weil|Weil, Henri]]. 1887. ''De l'ordre des mots dans les langues anciennes comparées aux langues modernes: question de grammaire générale.'' 1844. Published in English as ''The order of words in the ancient languages compared with that of the modern languages.''
{{refend}}

==External links==
* [http://www.alvinleong.info/sfg/sfgtheme.html SFG page: theme] – an explanation, for beginners, of theme in [[systemic functional grammar]] by Alvin Leong
* [http://www.ijors.net/issue7_1_2018/articles/iliev.html Iliev, Iv. The Russian Genitive of Negation and Its Japanese Counterpart. International Journal of Russian Studies. 1, 2018]

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[[Category:Systemic functional linguistics]]
[[Category:Word order]]
[[Category:Linguistics]]
[[Category:Dichotomies]]
[[Category:Semantics]]