  (1) and (3) are compatible; (2) may be a separate notion having more to do with the unity of definition and seems incompatible with (4); Aristotle treats (3) and (4) as the same notion. Since Aristotle's concern in discussing (4) is with the nature of the parts of definitions and not with questions of extended matter, it is unclear whether the non-definitional parts are potential extended parts or merely forms of extended parts, although the former seems more plausible.