# Formula Symbols - S

Written by Jerry Ratzlaff on . Posted in Nomenclature & Symbols for Engineering, Mathematics, and Science

## Formula Symbols

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## S

SymbolGreek SymbolDefinitionUSMetricValue
$$S_0/R$$ - Sackur-Tetrode constant dimensionless constant dimensionless constant $$-1.164\;8708$$
$$SF$$ - safety factor - - -
$$S$$ - sag $$in$$ $$mm$$ -
$$Q_s$$ - sand quantity - - -
$$r_s$$ - sand ratio - - -
$$\rho_{sat}$$ rho saturated bulk density of soil $$lb/gal$$ $$g/mL$$ -
$$\gamma_{sat}$$ gamma saturated unit weight $$lbf$$ $$N$$ -
$$e_s$$ - saturated vapor pressure $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$  -
$$\vartheta$$, $$\;\theta$$ vartheta, theta scattering angle - -  -
$$Sc$$ - Schmidt number dimensionless dimensionless  -
$$SEER$$ - seasonable energy efficiency ratio $$kW-hr\;/\;Btu$$ -  -
$$I$$ - second moment of area $$in^4$$ $$mm^4$$  -
$$c_2$$ - second radiation constant constant constant $$1.438\;776\;877...\;x\;10^{-2}\;m\;K$$
$$S$$ - section modulus

$$in^3$$

$$mm^3$$  -
$$S_{required}$$  - section modulus required not to exceed allowable bending stress $$in^3$$  $$mm^3$$   -
$$S_x$$  - section modulus with the respect to the x-centroidal axis $$in^3$$  $$mm^3$$   -
$$S_y$$  - section modulus with the respect to the y-centroidal axis $$in^3$$  $$mm^3$$   -
$$w_s$$ - sediment fall velocity - - -
$$v_s$$ - seepage velocity - -  -
$$L$$ - self-inductance - -  -
$$\delta$$ delta semivertex angle $$\deg$$ $$\deg$$  -
$$B$$ - separation distance $$ft$$ $$m$$  -
$$SF$$ - service factor - -  -
$$SC$$ - shading coefficient - -  -
$$F_s$$ - shading factor - -  -
$$d$$ - shaft deflection $$in$$ $$mm$$  -
$$k$$ - shape factor dimensionless dimensionless  -
$$J$$ - shear compliance - -  -
$$q$$ - shear flow $$lbf\;/\;in\;or\; kips\;/\;ft$$ $$N\;/\;m\;or\; kN\;/\;m$$  -
$$J"$$ - shear loss compliance - -  -
$$G"$$ - shear loss modulus $$Pa$$ $$Pa$$  -
$$G$$, $$\;\mu$$ mu shear modulus $$Pa$$ $$Pa$$  -
$$\dot {\gamma}$$ gamma shear rate - -  -
$$J'$$ - shear storage compliance - -  -
$$G'$$ - sheat storage modulus - -  -
$$\delta_s$$ delta shear deformation $$in$$ $$mm$$  -
$$V$$ - shear force $$lb \;,\; kip$$ $$N \;,\; kN$$  -
$$G$$ - shear modulus $$Pa$$ $$Pa$$  -
$$\dot {\gamma}$$ gamma shear rate $$1/s \;,\; rad/s$$ $$1/s \;,\; rad/s$$  -
$$\gamma$$ gamma shear strain $$rad$$ $$rad$$  -
$$\tau$$ tau shear stress $$lb\;/\;in^2 \;or\; psi$$ $$kg \;/\; cm^2$$  -
$$\tau_{butt}$$ tau sheat stress of weld $$lb\;/\;in^2 \;or\; psi$$ $$kg \;/\; cm^2$$ -
$$\tau_{\theta}$$ tau shear stress in any oblique plane $$lbf\;/\;ft^2$$ $$Pa$$  -
$$u*$$ - shear velocity - - -
$$\sigma$$ sigma sheat tension - -  -
$$Sh$$ - Sherwood number dimensionless dimensionless  -
$$\theta$$, $$\;\tau_*$$ - Shields parameter dimensionless dimensionless  -
$$\theta$$ theta shock semivertex angle $$\deg$$ $$\deg$$  -
$$\sigma$$ sigma short range order parameter - -  -
$$s$$ - side length $$ft$$ $$m$$  -
$$S$$ - sight distance for stopping or passing $$ft$$ $$m$$ -
$$\mu$$ mu simple viscosity $$lbf-sec\;/\;ft^2$$ $$Pa\cdot s$$  -
$$C_f$$ - skin friction coefficient dimensionless dimensionless  -
$$G$$ - slipping - -  -
$$m$$ - slope $$ft$$ $$m$$  -
$$l$$ - slope length $$ft$$ $$m$$ -
$$S$$ - slope steepness $$ft/sec$$ $$m/sec$$ -
$$\phi$$ phi slope of the deflection of a beam at a point degrees radians  -
$$\eta_s$$ eta slurry viscosity - -  -
$$K$$ - soil erodibility factor - - -
$$SCL$$ - solar cooling load factor $$Btu\;/\;hr-ft^2$$ $$W\;/\;m^2$$  -
$$\Omega$$, $$\;\omega$$ Omega, omega solid angle $$deg$$ $$rad$$  -
$$S$$ - Sommerfield number dimensionless dimensionless  -
$$a$$ - sound $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$W$$ - sound energy flux - -  -
$$L_w$$ - sound power level - -  -
$$u$$ - sound particle velocity - -  -
$$L_p$$ - sound pressure level - -  -
$$L$$ - span length under consideration $$in \;,\; ft$$ $$mm \;,\; m$$  -
$$U$$ - specific cutting energy $$lbf-ft \;/\; ft^3$$ $$J \;/\; m^3$$  -
$$h$$ - specific enthalpy $$Btu\;/\;lbm$$ $$kJ\;/\;kg$$  -
$$C_d$$ - specific flow coefficient - -  -
$$R$$ - specific gas constant constant constant  $$8.3145\;J\;mol^{-1}\;K^{-1}$$
$$SG$$ - specific gravity dimensionless dimensionless  -
$$SG$$, $$\;SG_g$$ - specific gravity of gas dimensionless dimensionless  -
$$SG$$, $$\;SG_l$$ - specific gravity of liquid dimensionless dimensionless  -
$$G_s$$ - specific gravity of soil dimensionless dimensionless -
$$c$$ - specific heat $$Btu\;/\;lb- ^\circ F$$ $$kJ\;/\;kg-K$$  -
$$Q$$, $$\;c_p$$ - specific heat capacity $$Btu\;/\;lb- ^\circ F$$ $$kJ\;/\;kg-K$$  -
$$C_p$$ - specific heat constant pressure $$ft-lbf\;/\;lb-^\circ F$$ $$J\;/\;kg-K$$  -
$$C_v$$ - specific heat constant volume $$ft-lbf\;/\;lb-^\circ F$$ $$J\;/\;kg-K$$  -
$$c_a$$ - specific heat of air $$Btu\;/\;lb- ^\circ F$$ $$J\;/\;kg-K$$  -
$$c_l$$ - specific heat of liquid $$Btu\;/\;lb- ^\circ F$$ $$J\;/\;kg-K$$  -
$$\gamma$$, $$\;\kappa$$, $$\;k$$ gamma, kappa specific heat ratio dimensionless dimensionless  -
$$F_k$$ - specific heat ratio factor - -  -
$$I_{sp}$$ - specific impulse $$sec$$ $$s$$  -
$$u$$ - specific internal energy $$Btu\;/\;lbm$$ $$kJ\;/\;kg$$  -
$$R_{\lambda}$$ lambda specific thermal resistance $$hr-^\circ F\;/\;Btu$$ $$K\;/\;W$$ -
$$\eta_{sp}$$ eta specific viscosity - -  -
$$v$$, $$\;\upsilon$$ upsilon specific volume $$ft^3\;/\;lbm$$ $$m^3\;/\;kg$$  -
$$\gamma$$ gamma specific weight $$lbf\;/\;ft^3$$ $$N\;/\;m^3$$  -
$$\gamma_a$$ gamma specific weight of air $$lbf\;/\;ft^3$$ $$N\;/\;m^3$$  -
$$f_{c}{'}$$ - specified 28 day compressive strength of concrete $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$ -
$$w_\lambda$$ - spectral concentration of radiant energy density - -  -
$$I_v$$ - spectral concentration of radiant intensity - -  -
$$K$$ - spectral luminous efficacy - -  -
$$V$$ - spectral luminous efficiency - -  -
$$u$$, $$\;v$$ - speed $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$s$$ - speed (rpm) - -  -
$$c$$ - speed of light in vacuum constant constant $$299\;792\;458\;x\;m\;/\;s$$
$$c$$ - speed of light wave velocity constant constant $$299\;792\;458\;x\;m\;/\;s$$
$$a$$ - speed of sound $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$S$$, $$\;s_i$$ - spin - -  -
$$L_c$$ - spring coil wire length $$in$$ $$mm$$ -
$$k$$, $$\;k_s$$ - spring constant $$lbf \;/\; ft$$ $$N \;/\; m$$  -
$$d_s$$ - spring displacement $$in$$ $$mm$$  -
$$d_s$$   spring deflection $$in$$ $$mm$$ -
$$E$$, $$\;E_s$$ - spring energy $$ft-lbf$$ $$J$$  -
$$F_s$$ - spring force $$lbf$$ N  -
$$k_s$$ - spring force constant constant constant  -
$$l_f$$ - spring free length $$in$$ $$mm$$ -
$$C$$ - spring index dimensionless dimensionless  -
$$D_i$$ - spring inside diameter $$in$$ $$mm$$ -
$$l_i$$ - spring installed length $$in$$ $$mm$$ -
$$P$$ - spring load $$lb$$ $$kg$$ -
$$n$$, $$\; n_a$$  - spring number of active coils - - -
$$l_o$$ - spring operating length $$in$$ $$mm$$  -
$$D_o$$ - spring outside diameter $$in$$ $$mm$$ -
$$p$$ - spring pitch $$in$$ $$mm$$ -
$$PE_s$$ - spring potential energy $$lbf \;/\; ft$$ $$J$$  -
$$n_s$$ - spring rate $$in$$ $$mm$$ -
$$n_t$$ - spring total number of coils - - -
$$L_t$$ - spring total wire length $$in$$ $$mm$$ -
$$G$$ - spring shear modulus of material $$Pa$$ $$Pa$$ -
$$\tau$$ tau spring shear stress $$lb\;/\;in^2 \;or\; psi$$ $$kg \;/\; cm^2$$ -
$$l_s$$ - spring solid length or shut length $$in$$ $$mm$$  -
$$C_s$$ - spring space between coils $$in$$ $$mm$$  -
$$d$$ - spring wire diameter $$in$$ $$mm$$ -
$$S$$, $$\;\sigma$$ - spring wire stress $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$ -
$$p_s$$ - stagnation pressure $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$  -
$$R*$$ - standard atmosphere constant constant  $$101\;325\;Pa$$
$$\sigma$$ sigma standard deviation - - -
$$g$$ - standard gravity constant constant $$9.806\;65\;m\;s^{-2}$$
$$g$$ - standard gravity acceleration constant constant  $$9.806\;65\;m\;s^{-2}$$
$$St$$ - Stanton number dimensionless dimensionless  -
$$h_{sd}$$ - static discharge head $$ft$$ $$m$$  -
$$SE$$ - static efficiency - -  -
$$f_s$$ - static friction $$lbf$$ $$N$$  -
$$\mu_s$$ mu static friction coefficient dimensionless dimensionless  -
$$h_s$$ - static head $$ft$$ $$m$$  -
$$SP$$ - static pressure $$in\;wg$$ $$Pa$$  -
$$h_{ss}$$ - static suction head $$ft$$ $$m$$  -
$$\rho_s$$ rho steam density $$lb \;/\; ft^3$$ $$kg \;/\; m^3$$  -
$$Q_s$$ - steam flow rate $$ft^3 \;/\; sec$$ $$m^3 \;/\; s$$  -
$$\Psi$$ Psi steam function - -  -
$$L$$, $$\;L_s$$ - steam latent heat $$Btu \;/\; lbm$$ $$J \;/\; kg$$  -
$$\Phi$$ Phi steam potential - -  -
$$v_s$$ - steam velocity $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$Ste$$ - Stefan number dimensionless dimensionless  -
$$\sigma$$ sigma Stefan-Boltzmann constant constant constant  $$5.670\;374\;419...\;x\;10^{-8}\;W\;m^{-2}\;K^{-4}$$
- - Stefan-Boltzmann law - - -
$$k$$ - stiffness $$lbf\;/\;ft$$ $$N\;/\;m$$  -
$$St$$ - Stokes' law - -  -
$$Stk$$, $$\;S_k$$ - Stokes number dimensionless dimensionless  -
$$SSD$$, $$\;S$$ - stopping sight distance $$ft$$ $$m$$ -
$$\epsilon$$ epsilon strain $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$  -
$$\epsilon_o$$ epsilon strain amplitude - -  -
$$U$$ - strain energy $$lbf-in\;/\;in^3$$ $$J\;/\;m^3$$  -
$$S$$ - strength $$lbf\;/\;in^2$$ $$Pa$$  -
$$K$$ - strength coefficient $$lbf\;/\;in^2$$ $$MPa$$  -
$$k$$ - strength derating factor - -  -
$$S$$, $$\;\sigma$$ sigma stress $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$  -
$$L$$ - stroke $$in$$ $$mm$$  -
$$L$$ - stroke length $$in$$ $$mm$$  -
$$S$$ - strength $$lbf\;/\;in^2$$ $$Pa$$  -
$$Sr$$ - Strouhal number dimensionless dimensionless  -
$$N$$ - Stuart number dimensionless dimensionless  -
$$SA$$ - suction specific speed available $$rpm$$ $$rpm$$  -
$$\Sigma$$ Sigma summation - -  -
$$S$$   Summerfeld number - -  -
sun age constant constant $$1.4420\;x\;10^{17}\;s$$
sun escape velocity constant constant $$6.176\;x\;10^2\;m\;s^{-1}$$
sun loss of mass due to elmag radiation constant constant $$4.273\;x\;10^{9}\;kg\;s^{-1}$$
sun luminous effect constant constant $$98\;lm\;kg^{-1}\;m^{-2}\;s^3$$
sun mass constant constant $$1.989\;10\;x\;10^{30}\;kg$$
sun mean density constant constant $$1.408\;x\;10^3\;kg\;m^3$$
sun mean radius constant constant $$6.9550\;x\;10^8\;m$$
sun photosphere temperature constant constant $$5778\;K$$
sun surface gravity on equator constant constant $$2.74\;x\;10^2\;m\;s^{-2}$$
sun total neutrino emissions constant constant $$1.830\;x\;10^{38}\;s^{-1}$$
sun volume constant constant $$1.412\;26\;x\;10^{27}\;m^3$$
$$H_c$$ - superconductor critical field strength - -  -
$$T_c$$ - superconductor critical transition temperature - -  -
$$\Delta$$ Delta superconductor energy gap - -  -
$$S$$ - surface area $$ft^2$$ $$m^2$$  -
$$\sigma$$ sigma surface change density - -  -
$$h_{pd}$$ - surface discharge pressure $$ft$$ $$m$$  -
$$S$$ - surface - -  -
$$S4S$$ - surface 4 sided - -  -
$$h_{ps}$$ - surface suction head $$ft$$ $$m$$  -
$$\pi$$ pi surface pressure $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$  -
$$T_s$$ - surface temperature $$^\circ F$$ $$C$$  -
$$\gamma$$, $$\;\sigma$$ gamma, sigma surface tension $$lbf\;/\;ft$$ $$N\;/\;m$$  -
$$B$$ - susceptance - -  -
$$s$$ - symmetry number - -  -
Symbol Greek Symbol Definition US Metric Value

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