Svedberg

In chemistry, a Svedberg unit or svedberg (symbol S, sometimes Sv) is a non-SI metric unit for sedimentation coefficients. The Svedberg unit offers a measure of a particle's size indirectly based on its sedimentation rate under acceleration (i.e. how fast a particle of given size and shape settles out of suspension). The svedberg is a measure of time, defined as exactly 10⁻¹³ seconds (100 fs).

For biological macromolecules like ribosomes, the sedimentation rate is typically measured as the rate of travel in a centrifuge tube subjected to high g-force.

The svedberg (S) is distinct from the SI unit sievert or the non-SI unit sverdrup, which also use the symbol Sv, and to the SI unit Siemens which uses the symbol S too. Provided by Wikipedia