Technology readiness levels (TRL) is a useful management tool for technology identification and evaluation. TRL represents an agreed way of maturity degree measurement, ranging from its initial idea to its commercialisation in the market. In general, they are supported by technology assessment studies that allow technology to be positioned in one of TRL level. They are based on a scale from 1 to 9 with 9 being the most mature technology.
Originally, this concept arose at NASA and, nowadays, its use has become widespread when applied to all kinds of financed projects through public R&D calls such as Horizon 2020.
More information: https://www.nasa.gov/directorates/heo/scan/engineering/technology/txt_accordion1.html