radiometry

Radiometry is a highly specialized technical term used almost exclusively within the fields of physics, astronomy, and optical engineering. It describes the quantitative measurement of electromagnetic radiation, distinguishing it from photometry, which only deals with the perception of light by the human eye.

As a field of study or a scientific discipline, the term is treated as an uncountable noun. It refers to the theoretical framework and practical application of measurement rather than a discrete object or a countable event.