mesh size

in polymer science
symbol: $\xi$; units: $\pu{nm}$, $\pu{m}$
https://doi.org/10.1351/goldbook.12231
Average distance between two adjacent entanglements on a given macromolecule in a semi-dilute solution, a concentrated solution, or bulk amorphous polymer.
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 90 [Terms] [Paper]