mass fraction of the dissolved or dispersed material, resulting from a network-forming polymerization or crosslinking process, that is constituted of molecules of finite (statistically definable) relative molecular masses.
Source:
PAC, 2007, 79, 1801. 'Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007)' on page 1806 (https://doi.org/10.1351/pac200779101801)