Abstract
Human beings use language to express their thoughts and ideas. Polysemy, i.e. a property that a linguistic form has more than one meaning, is common in a natural language system. This thesis attempts to furnish a cognitive perspective toward lexical semantics by the observations and analyses of related issues concerning shang (上) and xia (下). Polysemous words shang and xia can be used not only as locative words, but also as main verbs and verbal complements, and sense extension occurs ranging from spatial domain to non-spatial domain. The network of these related senses also attests to cognition as the foundation of linguistic analysis.The methodology adopted in this thesis is conceptual structure approach (Jackedoff 1983, 1990). The surface expressions concerning shang and xia are decomposed into a set of finite semantic elements, and the mapping from conceptual structures to surface forms are made possible by lexicalization patterns. Expressions of locative meaning are represented by image-schema in order to illustrate how we transform spatial configuration in physical world into linguistic forms.The mechanisms involved in sense extension are the notion of compositionality, metaphor, metonymy and inference from context or real world knowledge. The basic sense and extended senses form a radial structure category. Meanwhile, we also find that shang and xia are in the process of grammaticalization. Both sense extension and grammaticalization are motivated by the fact that vertical spatial notion is human beings' basic cognitive ability.