# Formula Symbols - R

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

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 SymbolDefinitionUSMetric
$$Q_e$$ - radiant energy - -
$$Q_r$$ - radiant heat - -
$$r$$ - radius $$in\;$$or$$\;ft$$ $$m$$
$$k$$ - radius of gyration $$ft$$ $$m$$
$$r$$ - ratio - -
$$k$$ - ratio of specific heat - -
$$Ra$$ - Rayleigh number dimensionless number dimensionless number
$$R$$ - reaction force $$lbf$$ $$N$$
$$p_r$$ - reduced pressure - -
$$\upsilon_r$$ upsilon reduced specific volume - -
$$T_r$$ - reduced temperature - -
$$x$$ - relative abundance - -
$$RD$$ - relative density dimensionless number dimensionless number
$$\phi$$ phi relative humidity - -
$$k$$ - relative roughness $$in$$ $$mm$$
$$E_r$$ - relativistic energy - -
$$m_r$$ - relativistic mass - -
$$p$$ - relativistic momentum - -
$$R$$ - resistance $$ohm$$ $$ohm$$
$$\Omega$$ omega resistance $$ohm$$ $$ohm$$
$$R$$ - resultant force $$lbf$$ $$N$$
$$Re$$ - Reynolds number dimensionless number dimensionless number
$$F_R$$ - Reynolds number factor - -
$$Ri$$ - Richardson number dimensionless number dimensionless number
$$C_{rr}$$ - rolling resistance dimensionless number dimensionless number
$$Ro$$ - Roshko number dimensionless number dimensionless number
$$Ro$$ - Rossby number dimensionless number dimensionless number
$$n$$ - rotational speed $$rpm$$ $$rpm$$