photon quantities

https://doi.org/10.1351/goldbook.P04638
A group of quantities characterizing electromagnetic radiation in terms of the number of photons. The symbols of photon quantities may be distinguished by adding a subscript p.
See also: radiant, luminous quantities
Source:
Green Book, 2nd ed., p. 30 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)