In the Beer Lambert Law (equation 3) the term IT/Io is called transmittance. This form of spectroscopy has a setup similar to the one used for Absorption. Reflectance spectroscopy is the study of light as a function of wavelength that has been reflected or scattered from a solid, liquid, or gas.
Definition of metadata: Data that serves to provide context or additional information about other data. For example, information about the title, subject, author, typeface, enhancements, and size of the data file of a ...
Metadata is data about data. In other words, it is data that is used to describe another item's content. The term metadata is often used in the context of Web pages, where it describes page content for a search engine.