Technical languages in antiquity consisted of metaphors and metonymies to a much larger extent than today. Another characteristic is the use of homonyms in different disciplines. These basic principles also become apparent in the semantic evolution of the concept of πεϱίoδoς.

In order to trace the origin and history of this concept, three lines are followed in this paper. First of all, the etymologies and definitions found in ancient rhetoric are investigated. We note that these are closely associated with the particular conception of the essence and effect of the periodic movement as a result of the concept of a circular representation. Consequently the designation πεϱίoδoς is induced by the following traits of the period: rhythmical framing, the splitting up into a tension-producing and a tension-releasing part, the prediction of the further course from inception as well as the architectonic joining of relatively independent individual parts into a higher aesthetic unity. Although the passages cited illuminate the essence of the period in antiquity, they do not lead any further as far as etymology is concerned; rather, they turn out to be nothing but later reflections.

The second approach to the subject matter consists in the investigation of those ancient rhetorical works in which the adjacent disciplines of rhetoric and poetics/metrics are compared with each other. It turns out that these passages of classical rhetoric are especially closely connected with presentations of the doctrine of πεϱίoδoς. As the present research shows, πεϱίoδoς is originally a metrical-poetic term. The concept was transferred by authors interested in approximating poetics and rhetoric and aspiring to reform and to aesheticize prose in accordance with rules analogous to those of poetic diction. In this connection Gorgias and Thrasymachus should be mentioned.

Finally, in order to clarify the question concerning the original meaning of the metrical term πεϱίoδoς, another etymology of the classical period is brought into play, which has thus far been overlooked. This etymology refers to the art of dancing. According to it, πεϱίoδoς appears to have referred originally, in accordance with the sense of the word, to the circular movement of the chorus around the altar. All other terminological interpretation derive from this one.

In conclusion, the semantic history of πεϱίoδoς makes it clear that text-linguistic investigation is required for the illumination of phenomena concerning language history.