In the Wikipedia entry of the term "radiodrome" for a pursuit curve, there arose a question about its original intended meaning: ῥᾴδιος+δρόμος, or radius+δρόμος. I have been unable to find suitable dictionary entries for the word, which might shed light on its earliest usage, appearance, and intended evocation in the neologism.

Is there an older attestation of the term? For example, "brachistochrone" goes back to the 17th century.

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    I believe Wikipedia's source for the etymology, ῥᾴδιος+δρόμος, is "The Mathematics of Pursuits and Evasion" by Paul J. Nahin. Contrary to what I originally thought, the article originally had the Laitn-Greek etymology, but it later updated it to the Greek (in 2016), and I believe the change was due to Nahin's book. Commented Oct 5, 2020 at 2:28
  • @ExpeditoBipes No; "radiodrome" does not appear in that book. Also, the German version gives "radius," not "ῥᾴδιος". Whoever had added ῥᾴδιος into the English version mislead the reader. Commented Apr 2 at 21:50

1 Answer 1


I've corrected the Wikipedia article and made it conform to the German version.

The term is derived from the Latin word radius and the Greek word dromos, for there is a radial component in its kinematic analysis.

The word must have been concocted by a few fans of Latin-Greek terminology in science, for that term is not used among experts. The usual terms are "Verfolgungskurve" in German and "curve of pursuit" in English and some variations in the same vein.

  • Do you have a source for this claim? It sounds eminently reasonable to me, but I see that the Wikipedia article had a pretty acrimonious debate about the issue, and your editing it in one way doesn't exactly settle the issue.
    – brianpck
    Commented Apr 2 at 21:09
  • You may wish to glance over Paul Nahin's book Chases and Escapes: The Mathematics of Pursuit and Evasion which is dedicated to this subject. You'll see the terms such as "radial distance," "radial acceleration" etc., nevertheless, "radiodrome" not once. Actually, all the mentions by search engines can be traced back to this Wikipedia article, never to a well-established source (one of whose link I've given in the answer). Furthermore, the German version has relevantly connected radio to v. lat. radius „Strahl“. It was the English version that had made the bizarre connection to ῥᾴδιος. Commented Apr 2 at 21:35

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