A topic-prominent language is a language that organizes its syntax so that sentences have a topic–comment (or theme–rheme) structure, in which the topic is the thing being talked about (predicated) and the comment is what is said about the topic. This structure is independent of the syntactic ordering of subject, verb and object, and may be marked by word order (typically using left dislocation to mention the topic as first thing in the sentence, followed by the comment), or by explicit morphology (as in Japanese with the clitic particle wa).
The difference between topic-prominent languages and non-topic-prominent languages is that topic marking is done syntactically or morphologically in the former, whereas in the latter it is often done through prosodic mechanisms such as intonation, stress, or similar suprasegmental cues.
The Lolo-Burmese language Lisu has been described as highly topic-prominent, and Sara Rosen has demonstrated that "while every clause has an identifiable topic, it is often impossible to distinguish subject from direct object or agent from patient. There are no diagnostics that reliably identify subjects (or objects) in Lisu." This ambiguity is demonstrated in the following example:
|Translation:||a. "People, they bite dogs."|
|b. "People, dogs bite them."|
|Transcription:||Zhāng Sān||wǒ||yǐjing||jiàn-guò||le.||Transcription:||wǒ||yǐjing||jiàn-guò||le||Zhāng Sān.|
|Gloss:||Zhang San||I||already||see-EXP||RES||Gloss:||I||already||see-EXP||RES||Zhang San.|
|Translation:||(As for) Zhang San, I've seen (him) already.||Translation:||I've already seen Zhang San.|
|Gloss:||"fish"-||"red snapper"-||"be delicious"-|
|Translation:||As for fish, red snapper is delicious.|
|Translation:||(As for) me, some horses: I caught them. -> It was me who caught some horses (I caught some horses)|