Teleology: The study of the ultimate purpose of the design of something in nature.
For example, "what is the true purpose of the nose?" is a teleological question and, to say that all evolutionary changes occur for a definite purpose is a teleological explanation of evolution.
"Teleology" comes from ancient Greek roots but it (and teleological) 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.