Spectroscopy is the study of the interaction between matter and radiative energy of different types (electromagnetic, acoustic, ion flux, etc). When we do not specify the nature of the radiative energy, we are talking about optical spectroscopy - the interaction between matter and light.

Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism. Later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency.

Spectrometer separates incoming light by wavelength in order to measure a property of that light. Modular spectrometers allow the user to adjust several facets of their system, such as wavelength range or resolution, to find the best fit for their application.

Monochromator separates incoming light into its component wavelengths, selecting only a very narrow bandwidth of interest to output. Spectrograph separates incoming light into its component wavelengths for recording and analysis.