A topic-prominent language is a language that organizes its syntax to emphasize the topic–comment structure of the sentence. The term is best known in American linguistics from Charles N. Li and Sandra Thompson, who distinguished topic-prominent languages, like Japanese and Korean, from subject-prominent languages, like English.
In Li and Thompson's (1976) view, topic-prominent languages have morphology or syntax that highlights the distinction between the topic and the comment (what is said about the topic). Topic–comment structure may be independent of the syntactic ordering of subject, verb and object.
Many topic-prominent languages share several syntactic features that have arisen because, in these languages, sentences are structured around topics rather than subjects and objects:
They tend to downplay the role of the passive voice, if a passive construction exists at all, since the main idea of passivization is to turn an object into a subject in languages where the subject is understood to be the topic by default.
They often have sentences with so-called "double subjects", actually a topic plus a subject. For example, the following sentence patterns are common in topic prominent languages:
(Japanese) Sono yashi-wa happa-ga ookii.
その ヤシは 葉っぱが 大きい。
"That palm tree (topic) leaves (subject) are big."
(Turkish) Evin duvarı kırmızıydı.
Home's (topic) wall (subject) was red.
(Mandarin) Zhège rén gèzi hěn gāo.
這個人 個子 很高/这个人 个子 很高。
"This person (topic) height (subject) tall."
They do not have articles, which are another way of indicating old vs. new information.
The distinction between subject and object is not reliably marked
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: