The purpose of this study is to identify the independence and substantiality of prefixes. Affixes are bound morphemes, not free morphemes, and belong to grammatical morphemes rather than lexical morphemes. However, prefixes belonging to subcategories of affixes often have lexical meanings that are difficult to distinguish from general roots, and at the same time, they are used freely from the roots. The independence and substantiality of these prefixes have been the main cause for discussion of the categorization and scope of the prefixes. This paper attempts to quantitatively study the prefix’s independence and substantiality by analyzing the prefix appearing in The new Yonsei written corpus. A total of 34 prefixes were found in The new Yonsei written corpus. Twenty-one of the 34 prefixes have been segmented with nouns at least once, and in particular, all the high ten prefixes have been found to be segmented with nouns. And every prefix has substantial meaning. As a result, it turned out that independence is a concept of degree and that all prefixes have substantiality. (Yonsei University)