The Communication Function Classification System (CFCS, www.cfcs.us)  provides 5 levels (CFCS I, II, III, IV, V) to describe everyday communication performance.  While originally developed for use with individuals with cerebral palsy, the CFCS is now being used to describe communication performance of individuals with any disability. CFCS English.

The CFCS provides a valid and reliable classification of communication performance and activity limitations that can be used for research and clinical purposes.

The CFCS is analogous and complementary to the Gross Motor Function Classification System (GMFCS-ER), the Manual Ability Classification System (MACS), and the Eating and Drinking Ability Classification System (EDACS).

Reference for the initial CFCS Development:    view article here
Hidecker, M.J.C., Paneth, N., Rosenbaum, P.L., Kent, R.D., Lillie, J., Eulenberg, J.B., Chester, K., Johnson, B., Michalsen, L., Evatt, M., & Taylor, K. (2011). Developing and validating the Communication Function Classification System (CFCS) for individuals with cerebral palsy, Developmental Medicine and Child Neurology. 53(8), 704-710. doi: 10.1111/j.1469-8749.2011.03996.x, PMC3130799.