| Si | the most anterior point on the lower contour of the sella turcica [point]; silicon |
|---|---|
| s | Greek lower case letter sigma; conductivity; cross section; millisecond; molecular type or bond; pop... |
| t | Greek lower case letter tau; life [of radioisotope]; relaxation time; shear stress; spectral transmi... |
| U&L | upper and lower |
| US/LS | upper strength/lower strength [ratio] |