See: half-width (of a band), line width
Sources:
Green Book, 2nd ed., p. 31 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2244 (https://doi.org/10.1351/pac199668122223)
See also:
Orange Book, 2nd ed., p. 226 (https://media.iupac.org/publications/analytical_compendium/)