# Formula Symbols - R

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

SymbolGreek SymbolDefinitionUSMetric
$$r$$ - 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 $$in$$ $$mm$$
$$R$$ - resistance $$ohm$$ $$ohm$$
$$\Omega$$ omega resistance $$ohm$$ $$ohm$$
$$R$$ - resultant force $$lbf$$ $$N$$
$$Re$$ - Reynolds number dimensionless number dimensionless number
$$Ri$$ - 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 $$rpm$$ $$rpm$$