A telos (from the Greek τέλοϛ for "end", "purpose", or "goal") is an end or purpose, in a fairly constrained sense used by philosophers such as Aristotle. It is the root of the term "teleology," roughly the study of purposiveness, or the study of objects with a view to their aims, purposes, or intentions. Teleology figures centrally in Aristotle's biology and in his Theory of Causes.
In Aristotle’s Theory of Causes Telos factors in the Final Cause. The Final Cause is that for the sake of which a thing exists or is done, including both purposeful and instrumental actions and activities. The final cause or telos is the purpose or end that something is supposed to serve, or it is that from which and that to which the change is. This also covers modern ideas of mental causation involving such psychological causes as volition, need, motivation or motives, rational, irrational, ethical, and all that gives purpose to behavior.