# Formula Symbols - I

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

## Formula Symbols

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

## I

SymbolGreek SymbolDefinitionEnglishMetricSIValue
$$R$$ - ideal gas constant $$\large{ \frac{lbf-ft}{lbmol-R} }$$ $$\large{ \frac{J}{kmol-K} }$$ $$J-kmol^{-1} - K^{-1}$$  $$8.31446261815324$$ $$\large{ \frac{J}{kmol-K} }$$
- - ideal gas law $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
- - ideal gas law with compressibility factor $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$lx$$ - illuminance - - - -
$$b$$ - impact parameter - - - -
$$Z_o$$ - impedance of vacuum $$\Omega$$ $$\Omega$$ $$kg-m^2-s^{-3}-A^{-2}$$ $$376.730\;313\;461...$$ $$\Omega$$
$$d$$, $$\;d_i$$ - impeller diameter $$in$$ $$mm$$ $$mm$$ -
$$I$$ - impulse $$lbf-sec$$ $$N-s$$ $$kg-m-s^{-1}$$ -
$$I$$ - impulse velocity $$lbf-sec$$ $$N-s$$ $$kg-m-s^{-1}$$ -
$$I$$ - impulse with time $$lbf-sec$$ $$N-s$$ $$kg-m-s^{-1}$$ -
$$H$$, $$\;L$$ - inductance $$H$$ $$H$$ $$kg-m^2-s^{-2}-A^{-2}$$ -
$$X_L$$ - inductive reactance $$H$$ $$H$$ $$kg-m^2-s^{-2}-A^{-2}$$ -
$$I_a$$ - initial abstraction $$in$$ $$mm$$ $$mm$$ -
$$a_i$$ - initial acceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$  $$m- s^{-2}$$ -
$$\omega_i$$ omega initial angular velocity $$\large{\frac{rad}{sec}}$$ $$\large{\frac{rad}{s}}$$  $$rad - s^{-1}$$ -
$$l_i$$ - initial length $$ft$$ or $$in$$ $$m$$ or $$mm$$ $$m$$ or $$mm$$ -
$$d_1$$ - initial maneuver distance $$ft$$ $$m$$ $$m$$ -
$$x_i$$ - initial position - - - -
$$T_i$$ - initial temperature $$F$$ $$C$$ $$x+273.15\;K$$ -
$$t_i$$ - initial time $$sec$$ $$s$$ $$s$$ -
$$v_i$$ - initial velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m- s^{-1}$$ -
$$V_i$$ - initial volume $$ft^3$$ or $$in^3$$ $$m^3$$ or $$mm^3$$ $$m^3$$ or $$mm^3$$ -
$$p_i$$ - inlet pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$E_i$$ - input energy $$lbf-ft$$ $$J$$ $$kg - m^2 - s^{-2}$$ -
$$W_i$$ - input work $$lbf-ft$$ $$J$$ $$kg - m^2 - s^{-2}$$ -
$$ID$$ - inside diameter $$in$$ $$mm$$ $$mm$$ -
$$ID$$ - inside diameter of pipe $$in$$ $$mm$$ $$mm$$ -
$$D_b$$ - inside diameter of valve body outlet $$in$$ $$mm$$ $$mm$$ -
$$D_p$$ - inside diameter of outlet pipe $$in$$ $$mm$$ $$mm$$ -
$$a_i$$ - instantaneous acceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$  $$m- s^{-2}$$   -
$$\alpha_i$$ alpha instantaneous angular acceleration $$\large{\frac{rad}{sec^2}}$$ $$\large{\frac{rad}{s^2}}$$  $$rad- s^{-2}$$   -
$$v_i$$ - instantaneous velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m- s^{-1}$$   -
$$P$$ - internal design pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$U$$ - internal energy $$Btu$$ $$J$$ $$kg - m^2 - s^{-2}$$ -
$$p_i$$ - internal pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$r_i$$ - internal radius $$in$$ $$mm$$ $$mm$$ -
$$e$$ - internal roughness $$in$$ $$mm$$ $$mm$$ -
$$d$$ - internal pipe diameter $$in$$ $$mm$$ $$mm$$ -
$$ISD$$ - intersection sight distance $$ft$$ $$m$$ $$m$$ -
$$G_0^{-1}$$ - inverse conductance quantum $$\Omega$$ $$\Omega$$ $$kg-m^2-s^{-3}-A^{-2}$$ $$12\;906.403\;72$$ $$\Omega$$
$$\alpha^{-1}$$ alpha inverse fine structure constant dimensionless $$137.035\;999\;084\;(21)$$
$$Ir$$, $$\;\xi$$ xi Iribarren number dimensionless -
$$\alpha$$ alpha isentropic compressibility - - - -
$$k$$ - isentropic exponent - - - -
$$\beta$$ beta isobaric compressibility - - - -
$$H$$ - isobaric process - enthalpy $$\large{\frac{Btu}{lbm}}$$ $$\large{\frac{kJ}{kg}}$$ $$kJ- kg^{-1}$$ -
$$S$$ - isobaric process - entropy $$\large{\frac{lbf-ft}{F}}$$   $$\large{\frac{J}{K}}$$ $$J- K^{-1}$$ -
$$\kappa$$ kappa isothermal compressibility - - - -
Symbol Greek Symbol Definition English Metric   Value

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