energeia Greek term coined by Aristotle and often translated as ‘activity’, ‘actuality’, and even ‘act’, but more literally rendered ‘(a state of) functioning’. Since for Aristotle the function of an object is its telos or aim, energeia can also be described as an entelecheia or realization (another coined term he uses interchangeably with energeia). So understood, it can denote either (a) something’s being functional, though not in use at the moment, and (b) something’s actually functioning, which Aristotle describes as a ‘first realization’ and ‘second realization’ respectively (On the Soul II.5). In general, every energeia is correlative to some dunamis, a capability or power to function in a certain way, and in the central books of the Metaphysics Aristotle uses the linkage between these two concepts to explain the relation of form to matter. He also distinguishes between energeia and kinesis (change or motion) (Metaphysics IX.6; Nicomachean Ethics X.4). A kinesis is defined by reference to its terminus (e.g., learning how to multiply) and is thus incomplete at any point before reaching its conclusion. An energeia, in contrast, is a state complete in itself (e.g., seeing). Thus, Aristotle says that at any time that I am seeing, it is also true that I have seen; but it is not true that at any time I am learning that I have learned. In Greek, this difference is not so much one of tense as of aspect: the perfect tense marks a ‘perfect’ or complete state, and not necessarily prior activity. See also ARISTOTL. V.C.