# Formula Symbols - A

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

## A

SymbolGreek SymbolDefinitionEnglishMetricSIValue
$$V_d$$ - Abbe number dimensionless  -
$$T$$   absolute dry bulb temperature - $$K$$ $$K$$ -
$$AH$$ - absolute humidity $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{g}{m^3}}$$ $$g - m^{-3}$$  -
$$p_a$$ - absolute pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$  -
$$\epsilon$$ epsilon absolute roughness $$in$$ $$mm$$ $$mm$$  -
$$T_a$$ - absolute temperature $$F$$ $$C$$ $$x+273.15\;K$$  -
$$R_t$$ - absolute thermal resistance - - - -
$$\mu$$ mu absolute viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$Pa-s$$ $$kg - m^{-1} - s^{-1}$$  -
$$\alpha$$ alpha absorptance - - -  -
$$\alpha$$ alpha absorptivity - - -  -
$$a$$ - acceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$m - s^{-2}$$  -
$$a$$ - acceleration from force $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$m - s^{-2}$$  -
$$g$$   acceleration of free fall $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$m - s^{-2}$$ -
$$g$$ - acceleration of gravity $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$ $$m - s^{-2}$$  $$9.806\;65$$ $$\large{\frac{m}{s^2}}$$
$$\omega$$ omega acentric factor dimensionless -
$$acfm$$ - ACFM $$\large{\frac{ft^3}{min}}$$ $$\large{\frac{m^3}{min}}$$ $$m^3 - ^min{-1}$$ -
$$\gamma$$ gamma activity coefficient dimensionless  -
$$E_a$$ - activation energy $$lbf-ft$$ $$J$$ $$kg - m^2 - s^{-2}$$  -
$$ACFM$$ - actual flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$m^3 - s^{-1}$$   -
$$e$$ - actual vapor pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$  -
$$l$$ - acoustic path length between tranducer faces $$ft$$ $$m$$ $$m$$  -
$$p$$ - acoustic pressure  $$\large{\frac{lbf-sec}{ft^2}}$$ $$Pa$$ $$kg-m^{-1}-s^{-1}$$  -
$$t_d$$ - accustic signal downstream travel time $$sec$$ $$s$$ $$s$$  -
$$t_u$$ - accustic signal downstream travel time $$sec$$ $$s$$ $$s$$  -
- - adjusts for the volume occupied by the gas particles $$in^3$$ $$mm^3$$ $$mm^3$$ -
$$N_a$$ - aeration number dimensionless  -
$$A$$ - affinity - - -  -
$$t$$ - age of concrete $$days$$ $$days$$  $$days$$ -
$$t_o$$ - age of concrete at loading $$days$$ $$days$$ $$days$$ -
$$t_c$$   age of concrete when drying starts at end of moist curing $$days$$ $$days$$ $$days$$ -
$$a$$ - aggregate content of concrete $$\large{\frac{lbm}{yd^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg - m^{-3}$$ -
$$A$$ - air $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$\alpha$$ alpha air content expressed as percentage dimensionless -
$$ACR$$ - air consumption rate $$\large{\frac{ft^3}{min}}$$ $$\large{\frac{m^3}{min}}$$ $$m^3-min^{-1}$$  -
$$A$$ - air content dimensionless -
$$CFM$$, $$\;Q_a$$ - air flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$m^3 - s^{-1}$$  -
$$Q_a$$ - air flow rate through piping $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$m^3 - s^{-1}$$  -
$$AFR$$ - air-fuel ratio dimensionless  -
$$AHP$$ - air horsepower $$\large{\frac{lbf-ft}{sec}}$$ $$\large{\frac{J}{s}}$$ $$J - s^{-1}$$  -
$$T_i$$ - air inlet temperature $$F$$ $$C$$ $$x+273.15\;K$$  -
$$m_a$$ - air mixture $$lbm$$ $$kg$$ $$kg$$  -
$$T_o$$ - air outlet temperature  $$F$$ $$C$$ $$x+273.15\;K$$  -
$$d$$ - air pipe sizing $$in$$ $$mm$$ $$mm$$ -
$$p$$ - air pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$p_l$$ - air pressure loss through piping $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$  -
$$F_a$$ - air resistance $$lbf$$ $$N$$ $$kg - m - s^{-2}$$ -
$$F_a$$ - air resistance of drag $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$F_a$$ - air resistance force $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$c_a$$ - air specific heat $$\large{\frac{Btu}{lbm-F}}$$ $$\large{\frac{kJ}{kg-K}}$$ $$kJ - kg^{-1} - K^{-1}$$   -
$$\gamma_a$$ gamma air specific weight $$\large{\frac{lbf}{ft^3}}$$ $$\large{\frac{N}{m^3}}$$  $$N - m^{-3}$$   -
$$v_a$$ - air velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$m - s^{-1}$$ -
$$v_a$$ - air velocity through piping $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$ -
$$s$$ - AGMA stress number - - -  -
$$Al$$ - Alfven number dimensionless  -
$$v_a$$ - Alfven speed $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$  -
$$A$$ - algebric difference in grade dimensionless -
$$F_a$$ - allowable axial stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$  -
$$F_b$$ - allowable bending stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$  -
$$F_c$$ - allowable compressive stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$  -
$$F_v$$ - allowable shear stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$  -
$$S$$ - allowable stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$  -
$$ASD$$ - allowable stress design $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$ -
$$S_a$$ - allowable stress range $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$ -
$$F_t$$ - allowable tensile stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$   -
$$A$$ - allowance - - -  -
$$m_a$$ - alpha particle mass $$lbm$$ $$kg$$ $$kg$$ $$6.644\;657\;230\;(82)\;x\;10^{-27}$$ $$kg$$
$$AC$$ - alternating current $$I$$ $$\large{\frac{C}{s}}$$ $$C - s^{-1}$$  -
$$V_{mixture}$$ - Amagat's law $$ft^3$$ $$m^3$$ $$m^3$$  -
$$T_a$$ - ambient temperature $$F$$ $$C$$ $$x+273.15\;K$$  -
$$n$$ - amount of substance - - -  -
$$A$$ - amp $$I$$ $$\large{\frac{C}{s}}$$ $$C - s^{-1}$$  -
$$A$$ - ampere $$I$$ $$\large{\frac{C}{s}}$$ $$C - s^{-1}$$  -
$$A$$ - amplitude $$in$$ $$mm$$  $$mm$$  -
$$A_l$$ - amplitude (longitudinal) $$in$$ $$mm$$ $$mm$$ -
$$AR$$ - amplitude ratio - - -  -
$$\beta$$ beta Andrade's beta - - -  -
$$\omega$$ omega angular frequency $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$ $$rad - s^{-1}$$ -
$$A$$, $$\;B$$, $$\;C$$ - Antoine constant - - -  -
- - Antoine equation $$\large{\frac{lbf}{in^2}}$$ $$\large{\frac{kg}{m-s^2}}$$  $$kg - m^{-1} - s^{-2}$$ -
$$A$$, $$\;\theta$$, $$\;deg$$ theta angle $$deg$$ $$rad$$ $$rad$$   -
$$\phi$$ phi angle $$deg$$ $$rad$$ $$rad$$   -
$$\theta$$ theta angle between a perpendicular vector to the area and the magnertic field $$deg$$ $$rad$$ $$rad$$  -
$$\theta$$ theta angle between acoustic path and the pipe's longitudinal axis $$deg$$ $$rad$$ $$rad$$   -
$$\Delta A$$ delta angle differential $$deg$$ $$rad$$ $$rad$$   -
$$Imp$$ - angle impulse $$lbf-ft-sec$$ $$N-m-s$$ $$N-m-s$$  -
$$\theta$$ theta angular rotation $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$  $$rad - s^{-1}$$  -
$$\gamma$$ gamma angle of twist $$deg$$ $$rad$$ $$rad$$   -
$$\alpha$$ alpha angular acceleration $$\large{\frac{deg}{sec^2}}$$ $$\large{\frac{rad}{s^2}}$$  $$rad - s^{-2}$$  -
$$\theta$$ theta angular deflection $$in$$ $$mm$$ $$mm$$  -
$$\theta$$ theta angular displacement $$deg$$ $$rad$$ $$rad$$  -
$$\omega$$ omega angular frequency $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$  $$rad - s^{-1}$$  -
$$H$$ - angular impulse  $$\large{\frac{lbm-ft^2}{sec}}$$  $$\large{\frac{kg-m^2}{s}}$$ $$kg-m^2-s^{-1}$$  -
$$L$$ - angular momentum  $$\large{\frac{lbm-ft^2}{sec}}$$  $$\large{\frac{kg-m^2}{s}}$$ $$kg-m^2-s^{-1}$$  -
$$L$$ - angular momentum of an object with linear momentum  $$\large{\frac{lbm-ft^2}{sec}}$$  $$\large{\frac{kg-m^2}{s}}$$  $$kg-m^2-s^{-1}$$ -
- - angular Planck constant  $$\large{\frac{lbf-ft}{sec}}$$ $$J-s$$ $$kg-m^2-s^{-1}$$ $$1.054\;571\;726\;(47)\;x\;10^{-34}$$ $$J-s$$
$$\theta$$ theta angular position $$deg$$ $$rad$$ $$rad$$  -
$$\omega_0$$ omega angular resonant frequency $$\large{\frac{1}{sec}}$$ $$\large{\frac{1}{s}}$$ $$1 - s^{-1}$$ -
$$\theta$$ theta angular rotation $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$ $$rad - s^{-1}$$  -
$$\omega$$ omega angular speed $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$ $$rad - s^{-1}$$  -
$$\omega$$, $$\;v_a$$ omega angular velocity $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$  $$rad - s^{-1}$$  -
$$d \omega$$, $$\;\Delta \omega$$ omega angular velocity differential $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$ $$rad - s^{-1}$$  -
$$\omega$$ omega angular velovity of a rolling sphere $$\large{\frac{deg}{sec}}$$ $$\large{\frac{rad}{s}}$$ $$rad - s^{-1}$$ -
$$k$$ - angular wavenumber $$\large{\frac{rad}{ft}}$$ $$\large{\frac{rad}{m}}$$ $$rad - m^{-1}$$  -
$$k$$ - angular wave vector - - -  -
$$API_{gravity}$$   API gravity $$F$$ $$C$$ $$x+273.15\;K$$ -
$$a$$ - apothem $$in$$ or $$ft$$ $$mm$$ or $$m$$ $$mm$$ or $$m$$  -
$$P$$ - applied concentrated load $$lbf$$ $$N$$ $$kg - m - s^{-2}$$ -
$$w$$ - applied distributed load $$lbf$$ $$N$$ $$kg-m-s^{-2}$$ -
$$F_a$$ - applied force $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$R$$ - applied stress $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$ -
$$Ar$$ - Archimedes number dimensionless  -
$$B$$ - Archimede's principle $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$E$$, $$\;V$$ - arc voltage $$V$$ $$V$$ $$kg - m^2 - s^{-3} - A^{-1}$$ -
$$\overset{\frown}{l}$$, $$\; l_a$$ - arc length $$in$$ or $$ft$$ $$mm$$ or $$m$$  $$mm$$ or $$m$$ -
$$A$$, $$\;S$$ - area $$in^2$$ or $$ft^2$$ $$mm^2$$ or $$m^2$$ $$mm^2$$ or $$m^2$$  -
$$A$$, $$\;A_c$$ - area cross-section $$in^2$$ or $$ft^2$$ $$mm^2$$ or $$m^2$$ $$mm^2$$ or $$m^2$$ -
$$A_{throat}$$ - area cross the throat of a weld $$in^2$$ or $$ft^2$$ $$mm^2$$ or $$m^2$$ $$mm^2$$ or $$m^2$$  -
$$A_d$$ - area differential $$in^2$$ or $$ft^2$$ $$mm^2$$ or $$m^2$$ $$mm^2$$ or $$m^2$$  -
$$f_a$$ - area gradient - - -  -
$$\Delta A$$  - area thermal expansion $$in^2$$ $$mm^2$$ $$mm^2$$   -
$$\alpha_a$$ alpha area thermal expansion coefficient $$\large{ \frac{in^2}{in^2\;F} }$$ $$\large{ \frac{mm^2}{mm^2-C} }$$ $$mm^2-mm^{-2}-C^{-1}$$  -
$$Ar$$ - Arrhenius number dimensionless  -
$$k$$ - Arrhenius equation - $$\large{ \frac{mol}{L-s} }$$ $$mol- L^{-1}-s^{-1}$$ -
$$\rho$$ rho atmosphere density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$kg-m^{-3}$$  -
$$p_a$$, $$\;p_{atm}$$ - atmospheric pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$  -
$$m_a$$ - atomic mass - - -  -
$$m_u$$ - atomic mass constant $$lbm$$ $$kg$$ $$kg$$ $$1.660\;539\;066\;60\;(50)\;x\;10^{-27}$$ $$kg$$
$$u$$ - atomic mass unit $$lbm$$ $$kg$$ $$kg$$  -
$$Z$$ - atomic number dimensionless  -
$$N$$ - atomic number density - $$\large{\frac{atoms}{cm^2}}$$ $$atoms-cm^{-2}$$ -
$$A$$ - atomic weight - - -  -
$$p_a$$ - atmospheric pressure $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$p_a$$ - atmospheric pressure of moist air $$\large{\frac{lbf}{in^2}}$$ $$Pa$$ $$kg- m^{-1}-s^{-2}$$ -
$$T_a$$ - atmospheric temperature $$F$$ $$C$$ $$x+273.15\;K$$ -
$$A$$ - Atwood number dimensionless  -
$$Nv$$ - Avagadro's number moles moles moles  -
$$\Phi$$ Phi availability function - - -  -
$$\bar {a}$$, $$\;a_a$$ - average acceleration $$\large{\frac{ft}{sec^2}}$$ $$\large{\frac{m}{s^2}}$$  $$m - s^{-2}$$   -
$$\bar {\alpha}$$ alpha average angular acceleration $$\large{\frac{deg}{sec^2}}$$ $$\large{\frac{rad}{s^2}}$$  $$rad - s^{-2}$$   -
$$v_a$$, $$\;\bar{\omega}$$ omega average angular velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$m - s^{-1}$$  -
$$v_a$$, $$\;\bar{\omega}$$ omega average angular velocity change in velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$ -
$$\bar {F}$$, $$\;F_a$$ - average force $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$mw$$ - average mole rate - - - -
$$\bar {u}$$, $$\;v_a$$ - average speed $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$m - s^{-1}$$  -
$$\sigma_{avg}$$ sigma average stress of weld $$\large{\frac{lbf}{in^2}}$$ $$MPa$$ $$N - mm^{-2}$$ -
$$\bar {v}$$, $$\;v_a$$ - average velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$m - s^{-1}$$  -
$$\bar{v}$$ - average velocity change in velocity $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$ -
$$v_a$$ - average axial velocity of water flow $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$  $$m - s^{-1}$$  -
- - Avogadro's law $$mol$$ $$mol$$ $$mol$$  -
$$L$$, $$\;N_a$$ - Avogadro constant $$\large{\frac{count}{mol}}$$ $$\large{\frac{count}{mol}}$$  $$count - mol^{-1}$$  $$6.022\;141\;29\;(27) \;x\; 10^{23}$$ $$\large{\frac{count}{mol}}$$
$$D_a$$ - axial diffusivity - - -  -
$$P$$ - axial force $$lbf$$ $$N$$ $$kg - m - s^{-2}$$  -
$$k$$ - axial stiffness $$lbf$$ $$N$$ $$kg - m - s^{-2}$$ -
$$F$$ - axial thrust $$lbf$$ $$N$$ $$kg - m - s^{-2}$$ -
$$\epsilon_a$$, $$\;\epsilon$$ epsilon axial strain (longitudinal strain) $$\large{\frac{in}{in}}$$ $$\large{\frac{mm}{mm}}$$  $$mm - mm^{-1}$$   -
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