Teleological: Serving an ultimate purpose in its design.
For example, "What is the true purpose of the nose?" That is a teleological question. For another example, to say that all evolutionary changes occur for a definite purpose is a teleological explanation of evolution.
"Teleological" comes from ancient Greek roots but did not enter English until the 18th century. It is a compound of the Greek "tele-, telos," meaning "end or purpose" + the ending "logos" meaning "the science or study of" = the study of the ends or purposes.