retardation factor, \(R_{\text{F}}\)

in planar chromatography
https://doi.org/10.1351/goldbook.R05353
Ratio of the distance travelled by the centre of the spot to the distance simultaneously travelled by the mobile phase: \[R_{\text{F}}=\frac{b}{a}\] By definition the \(R_{\text{F}}\) values are always less than unity. They are usually given to two decimal places. In order to simplify this presentation the \(hR_{\text{F}}\) values may be used: they correspond to the \(R_{\text{F}}\) values multiplied by 100. Ideally, \(R_{\text{F}}\) values are identical to the \(R\) values used in @C01182@.
Source:
PAC, 1993, 65, 819. (Nomenclature for chromatography (IUPAC Recommendations 1993)) on page 845 [Terms] [Paper]