The aim of the present study is to determine the different meanings of telos and teleoo and of their compounds and derivatives, to trace the semantic interrelations, synchronically and diachronically, and thus, hopefully, to discover the most likely etymology (or: etymologies, if in historical telos etc. two or more originally distinct roots should have merged). The period from which the data have been collected runs roughly from Homer down to the end of the 5th century B.C.