| p | Greek lower case letter pi; the ratio of circumference to diameter, 3.1415926536 |
|---|---|
| y | Greek letter psi; wave function |
| S | Greek capital letter sigma; syphilis; summation of series |
| 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... |