A Korean particle "-(n)un" is widely known as a topic and/or contrast marker. Despite this seemingly well-established view on the meaning/function of "-(n)un," however, its exact nature is far from clearly understood. The main purpose of this dissertation is to shed light on the meaning of "-(n)un," by looking at it from a different perspective, namely, the perspective of (discourse) salience. In unveiling the nature of "-(n)un," it is necessary to clearly understand the notions of information structure such as topic and contrast that are assumed to be marked by "-(n)un." It is also crucial to investigate the relation between these notions and "-(n)un." Unlike the standard view that posits direct relation between them, the dissertation provides strong evidence for indirect relation between "-(n)un" and topic/contrast. Based on a corpus study, I argue that what "-(n)un" really does is to IMPOSE SALIENCE on a discourse referent. Topicality and contrastiveness are only derived from the interaction of this meaning of "-(n)un" and various syntactic, semantic, and pragmatic factors. I support the proposed meaning of "-(n)un" by showing that 1) the main functions of "-(n)un" are introducing a new topic/frame, inducing contrast, and simply emphasizing a referent, 2) the use of "-(n)un" is constrained by the root restriction, and 3) different meanings expressed by "-(n)un" depending on its syntactic position are naturally explained by the proposed analysis of "-(n)un." Moreover, I further justify the meaning of "-(n)un" by comparing the pragmatic function of "-(n)un"-marked NPs with that of other types of NPs, that is, nominative-marked (or "-i/ka-" marked) NPs, bare NPs, and null NPs. Especially, I claim that the pragmatic meaning of -i/ka is UNIQUE SPECIFICATION of a referent, and the lack of this meaning in "-(n)un" is also crucial for understanding its nature. The dissertation also proposes that the meaning of imposing salience conveyed by "-(n)un" is not a truth-conditional (or at-issue) meaning, but must be captured under the formal framework that posits multiple dimensions of meaning. In particular, "-(n)un" is argued to express a kind of performative and is characterized as instructional meaning. The proposed analysis of "-(n)un" is further supported by the nature of contrastive implicatures it generates. Contrary to the standard view, which sees them as conventional implicatures, I argue that the contrastive implicature induced by "-(n)un" is conversational. Their conversational nature is backed up not only by semantic/pragmatic considerations but also by a prosodic experiment. If what is claimed in this dissertation is on the right track, it is not only helpful to gain an insight into the nature of "-(n)un," but it also has implications on information structure theory in general. Topic, focus, and contrast, although they are important notions for crosslinguistic studies, lose their status as UNIVERSAL categories (or primitives) of information structure. Instead, information structure of a particular language must be described in its own terms (e.g. imposing salience, unique specification). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]