Species formed by the rearrangement or fragmentation of a
primary species that is capable of initiating a polymerization.
Note:
The term 'secondary species' is also used to designate a species centred on a secondary carbon atom, e.g., a propan-2-yl radical.
See: primary species
Source:
PAC, 2022, 94, 1093. 'Terminology for chain polymerization (IUPAC Recommendations 2021)' on page 1125 (https://doi.org/10.1515/pac-2020-1211)