Abstract: Potential and Reality theory is an important part of Aristotle's philosophy. It has vital significance in Aristotle's solution of Being and Becoming. Moreover, it is the key point which helps us understand Aristotle's philosophy. This theory of Aristotle has been long known to our Chinese scholars, but that doesn't necessarily mean they have totally understood it. In fact, they haven't understood Aristotle's theory of potential reality thoroughly, which was caused by many reasons, one being that they didn't understand the word "δυναμls" correctly. This article believes the word "δυναμls", like the word "on", varies in meaning. Among the various meanings, the utmost one is "δυναμls"of "the power of changing" which can be further expanded and related to some other meanings. This article also argues that Aristotle himself once distinguished "δυναμls" in detail in the sense of the power of changing. The understanding into these distinguishes helps us better interpret some other philosophy theories of Aristotle. In a word, it is necessary for us to have a thorough understanding of Aristotle's "δυναμls". Otherwise, the understanding of potential and reality theory will pause to the surface level, and finally prevents us from better understanding the whole system of Aristotle's philosophy.