Modification is a morphological process which produces an alteration within a root or stem .
(English)
Matthews, P. H. 1991.Morphology. 2nd edition. Cambridge, England: Cambridge University.
Hartmann, R.R.K., and F.C. Stork. 1972.Dictionary of language and linguistics. London: Applied Science.
Crystal, David. 1985.A dictionary of linguistics and phonetics. 2nd edition. New York: Basil Blackwell.