# Formula Symbols - D

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

## Formula Symbols - D

For other symbols see:  A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

SymbolGreek SymbolDefinitionUSMetricValue
$$Da$$ - Damkohler number dimensionless dimensionless -
$$\delta$$, $$\;\lambda$$ delta , lambda dampening coefficient - - -
$$\zeta$$ zeta damping ratio dimensionless dimensionless -
$$f$$, $$\;C_f$$, $$\;f_d$$ - Darcy friction factor dimensionless dimensionless -
$$Da$$ - Darcy's law - - -
$$Da$$ - Darcy number dimensionless dimensionless -
$$DW$$ - Darcy-Weisbach equation dimensionless dimensionless -
$$D$$ - Dean number dimensionless dimensionless -
$$De$$ - Deborah number dimensionless dimensionless -
$$w_d$$ - Debye angular frequency - - -
$$q_d$$ - Debye angular wave number - - -
$$\lambda_d$$ lambda Debye length - - -
$$\Theta_d$$ Theta Debye temperature - - -
$$D$$ - Debye-Waller factor - - -
$$\lambda$$ lambda decay constant - - -
$$d$$ - deceleration $$ft\;/\;sec^2$$ $$m\;/\;s^2$$ -
$$dB$$ - decibel dimensionless dimensionless -
$$d$$, $$\; \delta$$ delta deflection - - -
$$\delta$$ delta deformation $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$x$$ - degree of ionization - - -
$$\mu$$ mu degree of saturation - - -
$$F$$ - degrees of freedom - - -
$$\rho$$ rho density $$lb\;/\;ft^3$$ $$kg\;/\;m^3$$ -
$$\rho_a$$ rho density of air - - -
$$\rho$$ rho density (aether) constant constant $$9.605125782\;x\;10^{24}\;kg\;/\;m^3$$
$$\rho_f$$ rho density (fluid) $$lb\;/\;ft^3$$ $$kg\;/\;m^3$$ -
$$\rho_v$$ rho density (vapor) $$lb\;/\;ft^3$$ $$kg\;/\;m^3$$ -
$$\rho$$ rho density of an ideal gas $$lb\;/\;ft^3$$ $$kg\;/\;m^3$$ -
$$N_e$$, $$\;\rho$$ rho density of state - - -
$$\rho_w$$ rho density of water - - -
$$z$$ - depth $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$\partial$$ partial derivative (rate of change) - - -
$$R^2$$ - determination coefficient dimensionless dimensionless -
$$T_d$$ - dewpoint temperature $$^\circ F$$ $$C$$
$$d$$ - diameter $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$\epsilon$$ epsilon dielectric constant - $$F\;/\;m$$ -
$$P$$ - dielectric polarization - - -
$$d$$, $$\;\Delta$$ delta differential - - -
$$D$$, $$\;D_n$$, $$\;D_p$$ - diffusion coefficient $$lbf$$ $$N$$ -
$$L_n$$, $$\;L_p$$ - diffusion length - - -
$$\alpha$$ alpha diffusivity $$ft^2\;/\;hr$$ $$m^2\;/\;s$$ -
$$a$$, $$\;b$$ - dimension $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$DA$$ - dimensional analysis - - -
$$k_d$$ - dimensional constant - - -
$$n$$ - dimensionless exponent - - -
$$K$$ - dimensionless factor - - -
$$N$$, $$DN$$ - dimensionless number - - -
$$\mu$$, $$\;C_d$$ mu discharge coefficient dimensionless dimensionless -
$$d$$, $$\;\vec{d}$$, $$\;s$$, $$\;\delta$$ delta displacement $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$\vec{D}$$ - displacement current - - -
$$\psi$$, $$\;\delta$$ psi, delta dissipation factor - - -
$$E_d$$ - dissociation energy - - -
$$d$$, $$\;l$$, $$\;x$$, $$\;y$$ - distance $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$s$$ - distance along cable $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$a$$ - distance to lowest cable point $$in \;or\; ft$$ $$mm \;or\; m$$ -
$$w$$ - distributed load $$lbf \;/\; ft$$ $$N \;/\; m$$ -
$$E_d$$ - donor ionization energy - - -
$$K_2$$ - downstream resistance coefficient dimensionless dimensionless -
$$D$$ - draft $$in-wg$$ kPa -
$$C_d$$ - drag coefficient dimensionless dimensionless -
$$F_d$$ - drag force $$lbf$$ $$N$$ -
$$v_{dr}$$ - drift velocity - - -
$$\zeta$$ zeta dryness fraction - - -
$$T_d$$ - dewpoint temperature $$F$$ $$C$$ -
$$Du$$ - Dukhin number dimensionless dimensionless -
$$Q$$, $$\;q$$ - dynamic pressure $$lb\;/\;in^2 \;or\; psi$$ $$Pa$$ -
$$a$$ - dynamic speed constant $$ft \;/\; min$$ - -
$$\mu$$, $$\;\eta$$ mu (used in mechanical), eta (used in chemical) dynamic viscosity $$ft-lbf\;/\;ft^2-sec$$ $$mPa-s$$ -