The United Nations’ agencies and many scholars have regarded traditional knowledge as an alternative to science for the purposes of managing the environment. Many countries have adopted this line of approach and formulated some policy strategies. A number of scholars also have engaged in traditional knowledge research and published their works. Despite a large number of publications on traditional knowledge, there seems to be little consensus about the definition of what traditional knowledge is and how it can be useful for environmental management. This article first approaches this definition problem within a historical context in order to clarify the core issues surrounding the definition of traditional knowledge.