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This article discusses about the different definitions of the category of quantity. From these definitions, the second and the third are zoomed on more. Because number is not a secondary philosophical intelligible. It is not also from the genus of existence. On the contrary, it exists in its object existence and it is a first intelligible. We demonstrate that number is of nature and the thing, which actually is divided, is object not number. Number is a thing although it can be divided. It also deduces that different numbers are species. We argue that the difference between connected quantity and separate quantity is not in defect division, but in having common component. We also criticize the argument that declares straight lines and curves are species.