Abstract: For a long time the randomness and the fuzziness are considered as the two aspects for explaining the uncerlain phenomena, but the roughness being introduced later promotes to form the triune framework for describing the uncertainty.The randomness is an objective attribute, but the fuzziness and the roughness arc related to human's cognitive activities so that are collectively known as the impreciseness. The impreciseness becomes a promising research direction for the uncertain phenomena. The impreciseness is the cost and defects which human have to bear when cognizing the uncertain objects,in detail,the fuzziness is the loss of clear understanding for a cognitive object in order to obtain the cognitive possibility and efficiency; the roughness is the lack of exact description for a cognitive object as to be explained approximativcly with two subsets of the existing knowledge set. The fuzziness is derived from the human's classifying cognitive objects, and the roughness from the imperfection of human's existing knowledge. The impreciseness has three primary properties; subjectivity, classifying-based, and relying on existing knowledge. To decrease the impreciseness should start with the existing knowledge, increasing the cauantity and improving the orderliness.

Key words: Impreciseness, Fuzziness, Roughness, Uncertainty