The classification of the symmetry elements of an object. It is denoted in the Schoenflies notation by an italic symbol, such as C3, D2, T d, etc.
Source:
PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2213 (https://doi.org/10.1351/pac199668122193)