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ronto-

A prefix for SI units, proposed in 2019 by Richard Brown¹, and submitted to the BIPM's Consultative Committee on Units. It would have the symbol r (lowercase) and represent 10⁻²⁷, that is, one rV would be one 1,000,000,000,000,000,000,000,000,000th of a volt.

The ronto- was offically adopted by a vote of the General Conference on Weights and Measures (CGPM) in Versailles, France on November 18, 2022.

Read more at the ANSI Blog: "New Prefixes in the SI: ronto, quecto, ronna, quetta

In the same proposal: quecca-, ronna-, quecto-.

1. Richard J. C. Brown.
On the nature of SI prefixes and the requirements for extending the available range.
Measurement, vol 137, pages 339-343 (April 2019).
doi:10.1016/j.measurement.2019.01.059