An Etymological Dictionary of Astronomy and Astrophysics

A thin → transition  → layer inside → Sun, between the → differentially rotating 
→ convection zone and the uniformly rotating → radiative zone.
Discovered through → helioseismology, it has raised considerable interest, but its thinness remains still to be explained. Due to its strong → shear, it is believed to play a crucial role in the generation of the → solar magnetic field.

Etymology (EN): Tachocline, from tacho- a combining form meaning “speed,” → tachyon + → -cline “slope.” The term was first coined by Edward A. Spiegel and Jean-Paul Zahn (1992, A&A 265, 106), by analogy to the oceanic → thermocline.

Etymology (PE): Tondâšib, from tondâ, → velocity, + šib, → -cline.