Technology readiness level (TRL) is a knowledge-based standard for evaluating the maturity of a technology or invention.
TRL 1 – Basic principles observed and reported: Scientific research results allow commencing applied research and technology development.
TRL 2 – Technology concept and/or application formulated.
TRL 3 – Experimental proof of concept: Active research and development is initiated (analytical/laboratory studies) to validate analytical predictions of separate elements of the technology.
TRL 4 – Technology validation in laboratory environment: Basic technological components are integrated to establish that they will work together in the laboratory environment.
TRL 5 – Technology validation in relevant environment: Technological components are integrated with reasonably realistic supporting elements so they can be tested in a simulated environment.
TRL 6 – Technology demonstration in relevant environment: A representative model or prototype is tested in a simulated environment.
TRL 7 – System prototype demonstration in operational environment: System prototype near or at planned operational system tested in an operational environment.
TRL 8 – System completed and qualified: Technology has been proven to work in its final form and under expected conditions (the last stage of technology development).
TRL 9 – Successful operation of the system.