root-mean-square end-to-end distance of a freely rotating chain

symbol: $\lt\!r_{\rm{o,f}}^{2}\!\gt^{1/2}$; units: $\pu{nm}$, $\pu{m}$
https://doi.org/10.1351/goldbook.12200
Root-mean-square end-to-end distance of a linear freely rotating chain.
Note: If no ambiguity results, the term "freely rotating end-to-end distance" can be used.
Source:
PAC, 2015, 87, 71. (Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)) on page 77 [Terms] [Paper]