Main Entry:

pho·ton

Pronunciation:

\ˈfō-ˌtän\

Function:

noun

Etymology:

phot- + ²-on

Date:

1916

1 : a unit of intensity of light at the retina equal to the illumination received per square millimeter of a pupillary area from a surface having a brightness of one candle per square meter 2 : a quantum of electromagnetic radiation

— pho·ton·ic \fō-ˈtä-nik\ adjective