There are multiple definitions:

1. soluble / serum [level](English)

   • sICAM-1, sVCAM-1
   • Clinical chemistry
   • https://doi.org…91.2004.01127.x

2. second(English)

   • duration of 9 192 631 770 periods of the radiation corresponding to the transition between the twohyperfine levels of the ground state of the caesium 133 atom
   • SI
   • Standards